Cleveland Clinic Journal of Medicine

Most of us have not spent the past 25 years on the front line continuously managing HIV-infected patients, but I am sure that at various points in our lives we all have been touched by the AIDS epidemic. Whether comforting a woman with knee pain in the office who is crying over the impending death of her son who lives in a group home for men with AIDS, diagnosing immune thrombocytopenia in a college student only to realize it is the seminal manifestation of his HIV infection, pleading unsuccessfully with several neurosurgeons to get one to perform a brain biopsy on an “enhancing ring lesion” in a young gay opera singer, or being part of a team caring for a gouty patient with AIDS and hepatitis C who had just undergone a successful liver transplantation, we all have our stories with resultant reflections on the era of medicine in which we practice.

In July 2012, the New York Times described the new home test for HIV infection as part of “the normalization of a disease once seen as a mark of shame.”¹ As with home pregnancy testing, people can now self-manage their need to know about what is going on in their body. But HIV goes so much deeper than this: it has been and remains a metaphor for and a reflection of many of the social issues that permeate our current political and social environment.

The politics and the social reactions to testing for HIV over the years since the virus was recognized in 1983–1984 is stuff for sociopsychologic treatises. Antibody testing was available in 1985, but in the absence of treatment, to test was simply to deliver a death sentence. Plus, with a diagnosis of AIDS, there would be no dental care, no insurance, no renting of an apartment, and perhaps no job. For some, family ties would be broken as closet doors would be thrown open, revealing a now unrecognized visage wearing the “mark of shame.” Some gay advocates rallied hard against testing, since anonymity and social protection for the infected could not be assured, a pragmatic response to blatant discrimination. In 1987, the first home test for HIV was in development, but—no surprise—there was no need for it.

As early treatments such as zidovudine (AZT) appeared and the value of specific antibiotic prophylaxis was demonstrated, there was some initial hope for treatment, and thus testing made medical sense. The size of the population infected (we were looking at the tip of the iceberg) was also being realized, so testing appealed to the social consciousness—try to limit infection. But discrimination wasn’t gone, and the politics of the time couldn’t quite handle all of the implications of a rapidly growing epidemic. America wasn’t ready for clean-needle-exchange programs, promotion of condom use, or open discussion of gay lifestyles. The Reagan White House was initially dead silent, except for proposing to limit entrance of potentially infected immigrants and promoting abstinence as the ideal protective approach.

Social righteousness took some hold, and protection of patient anonymity and autonomy became of paramount importance. But unintended consequences turned out to include limitation of testing: laws were written to require that HIV testing be accompanied by “appropriate,” stringently defined counseling, something that wasn’t always feasible. Patients needed to sign a release to be tested (“opt in”); many just said no. This tied the hands of physicians, so we developed work-arounds: we checked lymphocyte counts and CD4 counts to help us take care of patients too afraid to let us test for HIV directly.

Finally, in 2006, as therapies began to become increasingly effective and more data started to accumulate regarding the benefits of early antiretroviral therapy, the US Centers for Disease Control and Prevention recommended routine testing for all patients entering most acute health care facilities, unless they would actively decline (“opt out”). We have still not hit full stride in implementing universal testing for HIV. Nor have we hit our stride on fully accepting all demographic segments of the population. In some communities, HIV infection is still equivalent to the scarlet letter of Hester Prynne, not just because of the disease itself but because of the lifestyle it implies. Legislating laboratory testing practices cannot change all social attitudes. But maybe, hopefully, it is another step.

Dr. Christine Koval in this issue of the Journal discusses the practical use of the newly approved home HIV test. It is a short article, but it took a very, very long time for social and political forces to be modestly aligned sufficiently for there to be anything to write about. Since perhaps 18% of HIV-infected Americans are unaware of their infection, maybe some TV ads for this test, wedged between the ads for treating erectile dysfunction, can indeed bring (as the New York Times described) further “normalization” to the approach to managing HIV-infected patients.

Most of us have not spent the past 25 years on the front line continuously managing HIV-infected patients, but I am sure that at various points in our lives we all have been touched by the AIDS epidemic. Whether comforting a woman with knee pain in the office who is crying over the impending death of her son who lives in a group home for men with AIDS, diagnosing immune thrombocytopenia in a college student only to realize it is the seminal manifestation of his HIV infection, pleading unsuccessfully with several neurosurgeons to get one to perform a brain biopsy on an “enhancing ring lesion” in a young gay opera singer, or being part of a team caring for a gouty patient with AIDS and hepatitis C who had just undergone a successful liver transplantation, we all have our stories with resultant reflections on the era of medicine in which we practice.

In July 2012, the New York Times described the new home test for HIV infection as part of “the normalization of a disease once seen as a mark of shame.”¹ As with home pregnancy testing, people can now self-manage their need to know about what is going on in their body. But HIV goes so much deeper than this: it has been and remains a metaphor for and a reflection of many of the social issues that permeate our current political and social environment.

The politics and the social reactions to testing for HIV over the years since the virus was recognized in 1983–1984 is stuff for sociopsychologic treatises. Antibody testing was available in 1985, but in the absence of treatment, to test was simply to deliver a death sentence. Plus, with a diagnosis of AIDS, there would be no dental care, no insurance, no renting of an apartment, and perhaps no job. For some, family ties would be broken as closet doors would be thrown open, revealing a now unrecognized visage wearing the “mark of shame.” Some gay advocates rallied hard against testing, since anonymity and social protection for the infected could not be assured, a pragmatic response to blatant discrimination. In 1987, the first home test for HIV was in development, but—no surprise—there was no need for it.

As early treatments such as zidovudine (AZT) appeared and the value of specific antibiotic prophylaxis was demonstrated, there was some initial hope for treatment, and thus testing made medical sense. The size of the population infected (we were looking at the tip of the iceberg) was also being realized, so testing appealed to the social consciousness—try to limit infection. But discrimination wasn’t gone, and the politics of the time couldn’t quite handle all of the implications of a rapidly growing epidemic. America wasn’t ready for clean-needle-exchange programs, promotion of condom use, or open discussion of gay lifestyles. The Reagan White House was initially dead silent, except for proposing to limit entrance of potentially infected immigrants and promoting abstinence as the ideal protective approach.

Social righteousness took some hold, and protection of patient anonymity and autonomy became of paramount importance. But unintended consequences turned out to include limitation of testing: laws were written to require that HIV testing be accompanied by “appropriate,” stringently defined counseling, something that wasn’t always feasible. Patients needed to sign a release to be tested (“opt in”); many just said no. This tied the hands of physicians, so we developed work-arounds: we checked lymphocyte counts and CD4 counts to help us take care of patients too afraid to let us test for HIV directly.

Finally, in 2006, as therapies began to become increasingly effective and more data started to accumulate regarding the benefits of early antiretroviral therapy, the US Centers for Disease Control and Prevention recommended routine testing for all patients entering most acute health care facilities, unless they would actively decline (“opt out”). We have still not hit full stride in implementing universal testing for HIV. Nor have we hit our stride on fully accepting all demographic segments of the population. In some communities, HIV infection is still equivalent to the scarlet letter of Hester Prynne, not just because of the disease itself but because of the lifestyle it implies. Legislating laboratory testing practices cannot change all social attitudes. But maybe, hopefully, it is another step.

Dr. Christine Koval in this issue of the Journal discusses the practical use of the newly approved home HIV test. It is a short article, but it took a very, very long time for social and political forces to be modestly aligned sufficiently for there to be anything to write about. Since perhaps 18% of HIV-infected Americans are unaware of their infection, maybe some TV ads for this test, wedged between the ads for treating erectile dysfunction, can indeed bring (as the New York Times described) further “normalization” to the approach to managing HIV-infected patients.

Most of us have not spent the past 25 years on the front line continuously managing HIV-infected patients, but I am sure that at various points in our lives we all have been touched by the AIDS epidemic. Whether comforting a woman with knee pain in the office who is crying over the impending death of her son who lives in a group home for men with AIDS, diagnosing immune thrombocytopenia in a college student only to realize it is the seminal manifestation of his HIV infection, pleading unsuccessfully with several neurosurgeons to get one to perform a brain biopsy on an “enhancing ring lesion” in a young gay opera singer, or being part of a team caring for a gouty patient with AIDS and hepatitis C who had just undergone a successful liver transplantation, we all have our stories with resultant reflections on the era of medicine in which we practice.

In July 2012, the New York Times described the new home test for HIV infection as part of “the normalization of a disease once seen as a mark of shame.”¹ As with home pregnancy testing, people can now self-manage their need to know about what is going on in their body. But HIV goes so much deeper than this: it has been and remains a metaphor for and a reflection of many of the social issues that permeate our current political and social environment.

The politics and the social reactions to testing for HIV over the years since the virus was recognized in 1983–1984 is stuff for sociopsychologic treatises. Antibody testing was available in 1985, but in the absence of treatment, to test was simply to deliver a death sentence. Plus, with a diagnosis of AIDS, there would be no dental care, no insurance, no renting of an apartment, and perhaps no job. For some, family ties would be broken as closet doors would be thrown open, revealing a now unrecognized visage wearing the “mark of shame.” Some gay advocates rallied hard against testing, since anonymity and social protection for the infected could not be assured, a pragmatic response to blatant discrimination. In 1987, the first home test for HIV was in development, but—no surprise—there was no need for it.

As early treatments such as zidovudine (AZT) appeared and the value of specific antibiotic prophylaxis was demonstrated, there was some initial hope for treatment, and thus testing made medical sense. The size of the population infected (we were looking at the tip of the iceberg) was also being realized, so testing appealed to the social consciousness—try to limit infection. But discrimination wasn’t gone, and the politics of the time couldn’t quite handle all of the implications of a rapidly growing epidemic. America wasn’t ready for clean-needle-exchange programs, promotion of condom use, or open discussion of gay lifestyles. The Reagan White House was initially dead silent, except for proposing to limit entrance of potentially infected immigrants and promoting abstinence as the ideal protective approach.

Social righteousness took some hold, and protection of patient anonymity and autonomy became of paramount importance. But unintended consequences turned out to include limitation of testing: laws were written to require that HIV testing be accompanied by “appropriate,” stringently defined counseling, something that wasn’t always feasible. Patients needed to sign a release to be tested (“opt in”); many just said no. This tied the hands of physicians, so we developed work-arounds: we checked lymphocyte counts and CD4 counts to help us take care of patients too afraid to let us test for HIV directly.

Finally, in 2006, as therapies began to become increasingly effective and more data started to accumulate regarding the benefits of early antiretroviral therapy, the US Centers for Disease Control and Prevention recommended routine testing for all patients entering most acute health care facilities, unless they would actively decline (“opt out”). We have still not hit full stride in implementing universal testing for HIV. Nor have we hit our stride on fully accepting all demographic segments of the population. In some communities, HIV infection is still equivalent to the scarlet letter of Hester Prynne, not just because of the disease itself but because of the lifestyle it implies. Legislating laboratory testing practices cannot change all social attitudes. But maybe, hopefully, it is another step.

Dr. Christine Koval in this issue of the Journal discusses the practical use of the newly approved home HIV test. It is a short article, but it took a very, very long time for social and political forces to be modestly aligned sufficiently for there to be anything to write about. Since perhaps 18% of HIV-infected Americans are unaware of their infection, maybe some TV ads for this test, wedged between the ads for treating erectile dysfunction, can indeed bring (as the New York Times described) further “normalization” to the approach to managing HIV-infected patients.

In July 2012, the US Food and Drug Administration approved the first over-the-counter test kit for human immunodeficiency virus (HIV) infection, the OraQuick In-Home HIV Test (OraSure Technologies, Bethlehem, PA). This test is a variation of the currently available OraQuick ADVANCE Rapid HIV-1/2 Antibody Test used in clinical settings by trained personnel for rapid detection of HIV.

The home HIV test is expected to become available in the fall of 2012 from the company’s Web site and at retail drugstores. This will put the power of HIV testing into the hands of anyone able to afford the estimated $60 price and willing to purchase the item online or in stores.

GOAL: TO REDUCE THE NUMBER OF INFECTED PEOPLE WHO ARE UNAWARE

How home testing will change the demographics of HIV testing is not clear, but the intention is to reduce the number of HIV-infected people who are unaware of their infection and to get them in for care. Anthony Fauci, MD, the director of the National Institutes of Allergy and Infectious Diseases, has called the new test a “positive step forward” in bringing the HIV epidemic under control.¹

Recent figures from the US Centers for Disease Control and Prevention (CDC) indicate that, of the 1.2 million HIV-infected people in the United States, up to 220,000 are unaware of their infection.^2,3 Since antiretroviral therapy is now considered beneficial even in the early stages of HIV infection, those who are unaware of their infection are missing an opportunity for the most effective therapies.

They may also be unknowingly transmitting the virus, thus perpetuating the HIV epidemic. Awareness of one’s HIV infection may lead to behavioral changes that can reduce the risk of transmission. It has also become clear that antiretroviral therapy can dramatically reduce transmission rates, a concept known as “treatment as prevention.” ⁴ Thus, access to care and initiation of antiretroviral therapy have the potential to prevent progression to acquired immunodeficiency syndrome (AIDS) in the individual and to interrupt the spread of the virus in the community.

There are several steps between awareness of HIV infection and full engagement in HIV care that require attention from the health care community.⁵ Only a quarter of those with known HIV infection are in care and adherent to antiretroviral therapy, leaving much work to be done on removing barriers to effective treatment.⁵ The first step is still to identify those infected. The effort to increase the percentage of HIV-infected individuals who know their HIV status is one of the goals of the National HIV/AIDS Strategy and HealthyPeople2020.⁶

HOW THE TEST IS USED

The OraQuick In-Home Test consists of the device and reagents, instructional materials, information on interpreting the results, and contact information for the OraQuick Answer Center for information, support, and local medical referral.⁷ The overall time needed for testing is 20 to 40 minutes.

To perform the test, an oral fluid specimen is collected by swabbing the upper and lower buccal mucosa along the gum line. Once inserted into the developer solution the swabbed sample is carried onto a membrane strip containing HIV-1/2 antigens.

The device has two windows, one labelled “T” (for test) and the other labelled “C” (for control). If the patient has sufficient antibodies to HIV proteins, the “T” window indicates a positive result if a band is visible. The “C” (control) window displays a band to indicate if the device and reagents are working. If the control window does not show a band, then the kit has not functioned properly and the test result is not reliable.

SOME PEOPLE MAY STILL NEED HELP

For the test to succeed in informing people of their HIV status, it must be used effectively and the results must be interpretable. Of 5,662 participants in phase III investigational-device studies, 99% were able to use the kit and determine a result.⁷ While the test’s simplicity is similar to that of pregnancy test kits, it is possible that some people (at least 1% of those using the kit) may seek guidance from medical practitioners because they are unable to understand the test results.

For a test result to have the desired outcome of leading to HIV care, individuals must act on a positive result. When home test results are positive, the instructions indicate that “you may have HIV” and provide contact information for the OraQuick Answer Center. It is unclear how reliable the counseling, information, and referral process from OraSure will be and if people will use the service.

Individuals may access medical care at a variety of levels for further assistance if they have a positive test result. These may include primary care offices, emergency and urgent care settings, health departments, and HIV clinics.

LESS SENSITIVE THAN BLOOD TESTS

To provide additional care, clinicians must understand the performance of the home HIV test. Most importantly, the test result must be confirmed.

The In-Home test is less sensitive than currently available HIV blood tests used in the clinical setting, particularly the HIV-1/2 enzyme immunoassay (EIA) with confirmatory Western blot testing. The In-Home test is less likely to detect HIV infection during the 90-day “window period” when seroconversion is occurring, and so it should not be relied on to rule out HIV during this early period after infection.

The sensitivity and specificity of the OraQuick In-Home HIV test were determined in a phase III trial in 5,662 people (80% at risk of HIV), who were tested concurrently with the “gold standard” blood tests (EIA and Western blot). The sensitivity was 93% (giving a positive result in 106 of 114 patients who had a positive result on blood testing), and the specificity was 99.9% (giving a negative result in 5,384 of 5,385 patients who had a negative result on blood testing).⁷

Therefore, a positive In-Home test result is likely to be truly positive, but a negative result is not as reliably truly negative. False-negative results may occur particularly in the window period early after HIV infection, so the test should not be relied on within 90 days of high-risk behavior. In contrast, with the fourth-generation blood HIV tests, the window period is approximately 16 days.

The predictive value of the test will depend on the population using it and on the patient’s pretest probability of disease at the time of testing. In the population tested by OraQuick, the positive predictive value was 99.1% and the negative predictive value was 99.9%.⁷ Mathematical modeling has been done to examine the potential outcomes for use in subpopulations at lower risk and at higher risk.

As clinicians, we will have to address the potential for both false-positive and false-negative test results. False-positive results may be more likely in low-risk populations and may occur in the setting of cross-reactive antibodies from pregnancy, autoimmune diseases, or previous receipt of an experimental HIV vaccination. False-negative results may occur in the setting of acute HIV infection and in those with severely impaired immunity (eg, from agammaglobulinemia or immunosuppressive drugs) and will be more likely in higher-risk populations, such as men who have sex with men, intravenous drug users, blacks, and Hispanics ages 18 to 35 with multiple sexual partners. A positive In-Home HIV test should be followed up with a blood EIA and confirmed with Western blot in all patients.

WHO WILL USE THIS TEST?

It is unclear who will use this new test. In OraSure’s clinical trial, the percentages of people who indicated they would “definitely or probably buy” the test were:

• 20% of the general population
• 27% of those ages 18 to 35
• 49% of blacks ages 18 to 35
• 47% of homosexual men
• 43% of people who said they had more than two sexual partners per year
• 32% who said they use condoms inconsistently.

If this is true, the test may appropriately target several populations that are not currently being tested, either because they lack access to care or because they do not see themselves as being at high risk. Of those with newly diagnosed HIV infection from 2006 to 2009, 40% had had no prior testing, and the groups with the highest percentages of people in this category were black, men with injection drug use as their sole risk factor, those older than 50 years, and those with heterosexual contact as their sole risk factor.⁸ Because of difficulties in identifying some of these groups as “at risk,” the current CDC guidelines recommend that HIV testing be offered to all patients ages 13 to 64, regardless of their risk factors.⁹

The home HIV test may fill a gap in testing, extending it to those still not tested in the health care setting or to those who have not sought health care. For the home test to fill that gap, people still have to perceive themselves as at risk and then purchase the test. Through public health strategies and at clinical points of care, we must continue to inform our patients about HIV risk and work to identify new or ongoing risk factors that would prompt additional testing.

MANY QUESTIONS REMAIN

• Will those who need testing want to use this test? People will buy the test only if they perceive themselves to be at risk.
• Is this test affordable for the target populations? $60 will be unaffordable to some.
• Will the directions be followed effectively?
• Will home testing reduce opportunities to counsel patients on their HIV risk factors?
• Will there be situations in which individuals are socially pressured to take the test?
• Can users of the test expect the appropriate amount of privacy? Availability on the Internet and in drug stores is not a guarantee of privacy when purchasing the test, although the result presumably will not be known.
• Will those with positive results seek medical care?
• Will those with negative results who are still at high risk forgo more sensitive testing and continue to engage in high-risk activities?

Nevertheless, since early and continued treatment prevents disease progression and reduces HIV transmission, testing is the first step toward access to effective HIV care. The home HIV test is a step forward in providing high-quality HIV testing to the wider population.

In July 2012, the US Food and Drug Administration approved the first over-the-counter test kit for human immunodeficiency virus (HIV) infection, the OraQuick In-Home HIV Test (OraSure Technologies, Bethlehem, PA). This test is a variation of the currently available OraQuick ADVANCE Rapid HIV-1/2 Antibody Test used in clinical settings by trained personnel for rapid detection of HIV.

The home HIV test is expected to become available in the fall of 2012 from the company’s Web site and at retail drugstores. This will put the power of HIV testing into the hands of anyone able to afford the estimated $60 price and willing to purchase the item online or in stores.

GOAL: TO REDUCE THE NUMBER OF INFECTED PEOPLE WHO ARE UNAWARE

How home testing will change the demographics of HIV testing is not clear, but the intention is to reduce the number of HIV-infected people who are unaware of their infection and to get them in for care. Anthony Fauci, MD, the director of the National Institutes of Allergy and Infectious Diseases, has called the new test a “positive step forward” in bringing the HIV epidemic under control.¹

Recent figures from the US Centers for Disease Control and Prevention (CDC) indicate that, of the 1.2 million HIV-infected people in the United States, up to 220,000 are unaware of their infection.^2,3 Since antiretroviral therapy is now considered beneficial even in the early stages of HIV infection, those who are unaware of their infection are missing an opportunity for the most effective therapies.

They may also be unknowingly transmitting the virus, thus perpetuating the HIV epidemic. Awareness of one’s HIV infection may lead to behavioral changes that can reduce the risk of transmission. It has also become clear that antiretroviral therapy can dramatically reduce transmission rates, a concept known as “treatment as prevention.” ⁴ Thus, access to care and initiation of antiretroviral therapy have the potential to prevent progression to acquired immunodeficiency syndrome (AIDS) in the individual and to interrupt the spread of the virus in the community.

There are several steps between awareness of HIV infection and full engagement in HIV care that require attention from the health care community.⁵ Only a quarter of those with known HIV infection are in care and adherent to antiretroviral therapy, leaving much work to be done on removing barriers to effective treatment.⁵ The first step is still to identify those infected. The effort to increase the percentage of HIV-infected individuals who know their HIV status is one of the goals of the National HIV/AIDS Strategy and HealthyPeople2020.⁶

HOW THE TEST IS USED

The OraQuick In-Home Test consists of the device and reagents, instructional materials, information on interpreting the results, and contact information for the OraQuick Answer Center for information, support, and local medical referral.⁷ The overall time needed for testing is 20 to 40 minutes.

To perform the test, an oral fluid specimen is collected by swabbing the upper and lower buccal mucosa along the gum line. Once inserted into the developer solution the swabbed sample is carried onto a membrane strip containing HIV-1/2 antigens.

The device has two windows, one labelled “T” (for test) and the other labelled “C” (for control). If the patient has sufficient antibodies to HIV proteins, the “T” window indicates a positive result if a band is visible. The “C” (control) window displays a band to indicate if the device and reagents are working. If the control window does not show a band, then the kit has not functioned properly and the test result is not reliable.

SOME PEOPLE MAY STILL NEED HELP

For the test to succeed in informing people of their HIV status, it must be used effectively and the results must be interpretable. Of 5,662 participants in phase III investigational-device studies, 99% were able to use the kit and determine a result.⁷ While the test’s simplicity is similar to that of pregnancy test kits, it is possible that some people (at least 1% of those using the kit) may seek guidance from medical practitioners because they are unable to understand the test results.

For a test result to have the desired outcome of leading to HIV care, individuals must act on a positive result. When home test results are positive, the instructions indicate that “you may have HIV” and provide contact information for the OraQuick Answer Center. It is unclear how reliable the counseling, information, and referral process from OraSure will be and if people will use the service.

Individuals may access medical care at a variety of levels for further assistance if they have a positive test result. These may include primary care offices, emergency and urgent care settings, health departments, and HIV clinics.

LESS SENSITIVE THAN BLOOD TESTS

To provide additional care, clinicians must understand the performance of the home HIV test. Most importantly, the test result must be confirmed.

The In-Home test is less sensitive than currently available HIV blood tests used in the clinical setting, particularly the HIV-1/2 enzyme immunoassay (EIA) with confirmatory Western blot testing. The In-Home test is less likely to detect HIV infection during the 90-day “window period” when seroconversion is occurring, and so it should not be relied on to rule out HIV during this early period after infection.

The sensitivity and specificity of the OraQuick In-Home HIV test were determined in a phase III trial in 5,662 people (80% at risk of HIV), who were tested concurrently with the “gold standard” blood tests (EIA and Western blot). The sensitivity was 93% (giving a positive result in 106 of 114 patients who had a positive result on blood testing), and the specificity was 99.9% (giving a negative result in 5,384 of 5,385 patients who had a negative result on blood testing).⁷

Therefore, a positive In-Home test result is likely to be truly positive, but a negative result is not as reliably truly negative. False-negative results may occur particularly in the window period early after HIV infection, so the test should not be relied on within 90 days of high-risk behavior. In contrast, with the fourth-generation blood HIV tests, the window period is approximately 16 days.

The predictive value of the test will depend on the population using it and on the patient’s pretest probability of disease at the time of testing. In the population tested by OraQuick, the positive predictive value was 99.1% and the negative predictive value was 99.9%.⁷ Mathematical modeling has been done to examine the potential outcomes for use in subpopulations at lower risk and at higher risk.

As clinicians, we will have to address the potential for both false-positive and false-negative test results. False-positive results may be more likely in low-risk populations and may occur in the setting of cross-reactive antibodies from pregnancy, autoimmune diseases, or previous receipt of an experimental HIV vaccination. False-negative results may occur in the setting of acute HIV infection and in those with severely impaired immunity (eg, from agammaglobulinemia or immunosuppressive drugs) and will be more likely in higher-risk populations, such as men who have sex with men, intravenous drug users, blacks, and Hispanics ages 18 to 35 with multiple sexual partners. A positive In-Home HIV test should be followed up with a blood EIA and confirmed with Western blot in all patients.

WHO WILL USE THIS TEST?

It is unclear who will use this new test. In OraSure’s clinical trial, the percentages of people who indicated they would “definitely or probably buy” the test were:

• 20% of the general population
• 27% of those ages 18 to 35
• 49% of blacks ages 18 to 35
• 47% of homosexual men
• 43% of people who said they had more than two sexual partners per year
• 32% who said they use condoms inconsistently.

If this is true, the test may appropriately target several populations that are not currently being tested, either because they lack access to care or because they do not see themselves as being at high risk. Of those with newly diagnosed HIV infection from 2006 to 2009, 40% had had no prior testing, and the groups with the highest percentages of people in this category were black, men with injection drug use as their sole risk factor, those older than 50 years, and those with heterosexual contact as their sole risk factor.⁸ Because of difficulties in identifying some of these groups as “at risk,” the current CDC guidelines recommend that HIV testing be offered to all patients ages 13 to 64, regardless of their risk factors.⁹

The home HIV test may fill a gap in testing, extending it to those still not tested in the health care setting or to those who have not sought health care. For the home test to fill that gap, people still have to perceive themselves as at risk and then purchase the test. Through public health strategies and at clinical points of care, we must continue to inform our patients about HIV risk and work to identify new or ongoing risk factors that would prompt additional testing.

MANY QUESTIONS REMAIN

• Will those who need testing want to use this test? People will buy the test only if they perceive themselves to be at risk.
• Is this test affordable for the target populations? $60 will be unaffordable to some.
• Will the directions be followed effectively?
• Will home testing reduce opportunities to counsel patients on their HIV risk factors?
• Will there be situations in which individuals are socially pressured to take the test?
• Can users of the test expect the appropriate amount of privacy? Availability on the Internet and in drug stores is not a guarantee of privacy when purchasing the test, although the result presumably will not be known.
• Will those with positive results seek medical care?
• Will those with negative results who are still at high risk forgo more sensitive testing and continue to engage in high-risk activities?

Nevertheless, since early and continued treatment prevents disease progression and reduces HIV transmission, testing is the first step toward access to effective HIV care. The home HIV test is a step forward in providing high-quality HIV testing to the wider population.

In July 2012, the US Food and Drug Administration approved the first over-the-counter test kit for human immunodeficiency virus (HIV) infection, the OraQuick In-Home HIV Test (OraSure Technologies, Bethlehem, PA). This test is a variation of the currently available OraQuick ADVANCE Rapid HIV-1/2 Antibody Test used in clinical settings by trained personnel for rapid detection of HIV.

The home HIV test is expected to become available in the fall of 2012 from the company’s Web site and at retail drugstores. This will put the power of HIV testing into the hands of anyone able to afford the estimated $60 price and willing to purchase the item online or in stores.

GOAL: TO REDUCE THE NUMBER OF INFECTED PEOPLE WHO ARE UNAWARE

How home testing will change the demographics of HIV testing is not clear, but the intention is to reduce the number of HIV-infected people who are unaware of their infection and to get them in for care. Anthony Fauci, MD, the director of the National Institutes of Allergy and Infectious Diseases, has called the new test a “positive step forward” in bringing the HIV epidemic under control.¹

Recent figures from the US Centers for Disease Control and Prevention (CDC) indicate that, of the 1.2 million HIV-infected people in the United States, up to 220,000 are unaware of their infection.^2,3 Since antiretroviral therapy is now considered beneficial even in the early stages of HIV infection, those who are unaware of their infection are missing an opportunity for the most effective therapies.

They may also be unknowingly transmitting the virus, thus perpetuating the HIV epidemic. Awareness of one’s HIV infection may lead to behavioral changes that can reduce the risk of transmission. It has also become clear that antiretroviral therapy can dramatically reduce transmission rates, a concept known as “treatment as prevention.” ⁴ Thus, access to care and initiation of antiretroviral therapy have the potential to prevent progression to acquired immunodeficiency syndrome (AIDS) in the individual and to interrupt the spread of the virus in the community.

There are several steps between awareness of HIV infection and full engagement in HIV care that require attention from the health care community.⁵ Only a quarter of those with known HIV infection are in care and adherent to antiretroviral therapy, leaving much work to be done on removing barriers to effective treatment.⁵ The first step is still to identify those infected. The effort to increase the percentage of HIV-infected individuals who know their HIV status is one of the goals of the National HIV/AIDS Strategy and HealthyPeople2020.⁶

HOW THE TEST IS USED

The OraQuick In-Home Test consists of the device and reagents, instructional materials, information on interpreting the results, and contact information for the OraQuick Answer Center for information, support, and local medical referral.⁷ The overall time needed for testing is 20 to 40 minutes.

To perform the test, an oral fluid specimen is collected by swabbing the upper and lower buccal mucosa along the gum line. Once inserted into the developer solution the swabbed sample is carried onto a membrane strip containing HIV-1/2 antigens.

The device has two windows, one labelled “T” (for test) and the other labelled “C” (for control). If the patient has sufficient antibodies to HIV proteins, the “T” window indicates a positive result if a band is visible. The “C” (control) window displays a band to indicate if the device and reagents are working. If the control window does not show a band, then the kit has not functioned properly and the test result is not reliable.

SOME PEOPLE MAY STILL NEED HELP

For the test to succeed in informing people of their HIV status, it must be used effectively and the results must be interpretable. Of 5,662 participants in phase III investigational-device studies, 99% were able to use the kit and determine a result.⁷ While the test’s simplicity is similar to that of pregnancy test kits, it is possible that some people (at least 1% of those using the kit) may seek guidance from medical practitioners because they are unable to understand the test results.

For a test result to have the desired outcome of leading to HIV care, individuals must act on a positive result. When home test results are positive, the instructions indicate that “you may have HIV” and provide contact information for the OraQuick Answer Center. It is unclear how reliable the counseling, information, and referral process from OraSure will be and if people will use the service.

Individuals may access medical care at a variety of levels for further assistance if they have a positive test result. These may include primary care offices, emergency and urgent care settings, health departments, and HIV clinics.

LESS SENSITIVE THAN BLOOD TESTS

To provide additional care, clinicians must understand the performance of the home HIV test. Most importantly, the test result must be confirmed.

The In-Home test is less sensitive than currently available HIV blood tests used in the clinical setting, particularly the HIV-1/2 enzyme immunoassay (EIA) with confirmatory Western blot testing. The In-Home test is less likely to detect HIV infection during the 90-day “window period” when seroconversion is occurring, and so it should not be relied on to rule out HIV during this early period after infection.

The sensitivity and specificity of the OraQuick In-Home HIV test were determined in a phase III trial in 5,662 people (80% at risk of HIV), who were tested concurrently with the “gold standard” blood tests (EIA and Western blot). The sensitivity was 93% (giving a positive result in 106 of 114 patients who had a positive result on blood testing), and the specificity was 99.9% (giving a negative result in 5,384 of 5,385 patients who had a negative result on blood testing).⁷

Therefore, a positive In-Home test result is likely to be truly positive, but a negative result is not as reliably truly negative. False-negative results may occur particularly in the window period early after HIV infection, so the test should not be relied on within 90 days of high-risk behavior. In contrast, with the fourth-generation blood HIV tests, the window period is approximately 16 days.

The predictive value of the test will depend on the population using it and on the patient’s pretest probability of disease at the time of testing. In the population tested by OraQuick, the positive predictive value was 99.1% and the negative predictive value was 99.9%.⁷ Mathematical modeling has been done to examine the potential outcomes for use in subpopulations at lower risk and at higher risk.

As clinicians, we will have to address the potential for both false-positive and false-negative test results. False-positive results may be more likely in low-risk populations and may occur in the setting of cross-reactive antibodies from pregnancy, autoimmune diseases, or previous receipt of an experimental HIV vaccination. False-negative results may occur in the setting of acute HIV infection and in those with severely impaired immunity (eg, from agammaglobulinemia or immunosuppressive drugs) and will be more likely in higher-risk populations, such as men who have sex with men, intravenous drug users, blacks, and Hispanics ages 18 to 35 with multiple sexual partners. A positive In-Home HIV test should be followed up with a blood EIA and confirmed with Western blot in all patients.

WHO WILL USE THIS TEST?

It is unclear who will use this new test. In OraSure’s clinical trial, the percentages of people who indicated they would “definitely or probably buy” the test were:

• 20% of the general population
• 27% of those ages 18 to 35
• 49% of blacks ages 18 to 35
• 47% of homosexual men
• 43% of people who said they had more than two sexual partners per year
• 32% who said they use condoms inconsistently.

If this is true, the test may appropriately target several populations that are not currently being tested, either because they lack access to care or because they do not see themselves as being at high risk. Of those with newly diagnosed HIV infection from 2006 to 2009, 40% had had no prior testing, and the groups with the highest percentages of people in this category were black, men with injection drug use as their sole risk factor, those older than 50 years, and those with heterosexual contact as their sole risk factor.⁸ Because of difficulties in identifying some of these groups as “at risk,” the current CDC guidelines recommend that HIV testing be offered to all patients ages 13 to 64, regardless of their risk factors.⁹

The home HIV test may fill a gap in testing, extending it to those still not tested in the health care setting or to those who have not sought health care. For the home test to fill that gap, people still have to perceive themselves as at risk and then purchase the test. Through public health strategies and at clinical points of care, we must continue to inform our patients about HIV risk and work to identify new or ongoing risk factors that would prompt additional testing.

MANY QUESTIONS REMAIN

• Will those who need testing want to use this test? People will buy the test only if they perceive themselves to be at risk.
• Is this test affordable for the target populations? $60 will be unaffordable to some.
• Will the directions be followed effectively?
• Will home testing reduce opportunities to counsel patients on their HIV risk factors?
• Will there be situations in which individuals are socially pressured to take the test?
• Can users of the test expect the appropriate amount of privacy? Availability on the Internet and in drug stores is not a guarantee of privacy when purchasing the test, although the result presumably will not be known.
• Will those with positive results seek medical care?
• Will those with negative results who are still at high risk forgo more sensitive testing and continue to engage in high-risk activities?

Nevertheless, since early and continued treatment prevents disease progression and reduces HIV transmission, testing is the first step toward access to effective HIV care. The home HIV test is a step forward in providing high-quality HIV testing to the wider population.

In this article, we seek to convince you to measure the ankle-brachial index for any patient you suspect may have peripheral artery disease. This would include patients who are elderly, who smoke, or who have diabetes, regardless of whether or not they have symptoms. The ankle-brachial index is a simple test that involves taking the blood pressure in all four limbs using a hand-held Doppler device and then dividing the leg systolic pressure by the arm systolic pressure.

This simple test is both sensitive and specific for peripheral artery disease. It also gives a good assessment of cardiovascular risk. The downside: you or a member of your staff spends a few minutes doing it. Also, for patients without leg symptoms or abnormal findings on physical examination, you may not be paid for doing it.

Despite these limitations, the ankle-brachial index is a powerful clinical tool that deserves to be performed more often in primary care.

PERIPHERAL ARTERY DISEASE IS COMMON AND SERIOUS

Peripheral artery disease is important to detect, as it is common, it has serious consequences, and effective treatments are available. However, many patients with the disease do not have typical symptoms.

Peripheral artery disease affects up to 29% of people over age 70, depending on the population sampled.^1,2 Its classic symptom is intermittent claudication, ie, leg pain with walking that improves with rest. However, most patients do not have intermittent claudication; they have atypical leg symptoms or no symptoms at all.^2,3 While the risk factors for peripheral artery disease are similar to those for coronary artery disease, the factors most strongly associated with peripheral artery disease are older age, tobacco smoking, and diabetes mellitus.⁴ Blacks are twice as likely to have it compared with whites, even after adjusting for other cardiovascular risk factors.⁵

Untreated peripheral artery disease may have serious consequences, such as amputation, impaired functional capacity, poor quality of life, and depression.^3,6,7 In addition, it is a strong marker of atherosclerotic burden and cardiovascular risk and has been recognized as a coronary risk equivalent. Patients with peripheral artery disease are at higher risk of death, myocardial infarction, stroke, and hospitalization, with event rates as high as 21% per year.⁸

Fortunately, simple therapies have been shown to prevent adverse cardiovascular events in peripheral artery disease, including antiplatelet drugs, statins, and angiotensin-converting enzyme inhibitors.^9–11

THE ANKLE-BRACHIAL INDEX IS SENSITIVE AND SPECIFIC

The evaluation for possible peripheral artery disease should begin with the medical history, a cardiovascular review of systems, and a focused physical examination in which one should:

• Measure the blood pressure in both arms to assess for occult subclavian stenosis
• Auscultate for bruits over the carotid, abdominal, and femoral arteries
• Palpate the pulses in the lower extremities and the abdominal aorta
• Inspect the bare legs and feet for thinning of the skin, hair loss, thickening of the nails (which are nonspecific signs), and ulceration.

However, the physical examination has limited sensitivity and specificity for diagnosing peripheral artery disease. In general, the most reliable finding is the absence of a palpable posterior tibial artery pulse, which has been reported to have a specificity of 71% and a sensitivity of 91% for peripheral artery disease.¹²

The ankle-brachial index is the first-line test for both screening for peripheral artery disease and for diagnosing it. It is inexpensive and noninvasive to obtain and has a high sensitivity (79% to 95%) and specificity (95% to 96%) compared with angiography as the gold standard.^13–18 It can be measured easily in the office, and every practitioner who cares for patients at risk of cardiovascular disease can be trained to measure it competently.

HOW TO MEASURE THE ANKLE-BRACHIAL INDEX

The ankle-brachial index is the ratio of the systolic pressure in the ankle to the systolic pressure in the arm. In healthy people, this ratio is typically greater than 1.0 or 1.1.

You can measure the ankle-brachial index in the office with a blood pressure cuff, sphygmomanometer, and handheld Doppler device. Alternatively, it can be measured in a noninvasive vascular laboratory as part of a more detailed examination that allows for assessment of blood pressures and waveforms (Doppler or pulse-volume recordings) at multiple segments along the limb. These more detailed vascular studies are generally reserved for patients with confirmed peripheral artery disease to locate the level and extent of blockage or for patients in whom lower-extremity revascularization is contemplated.

The use of a stethoscope to measure blood pressures for the ankle-brachial index has been studied in a few small series,^19,20 but is thought to be less accurate than Doppler, especially in the setting of significant arterial occlusive disease. Because of this, it is recommended and assumed that a Doppler device be used to measure all blood pressures for the ankle-brachial index.

Information based on 2011 Writing Group Members, et al. 2011 ACCF/AHA focused update of the guideline for the management of patients with peripheral artery disease. Circulation 2011; 124:2020–2045.

After the patient has been resting quietly for 5 to 10 minutes in the supine position, the systolic blood pressure is measured in both arms and in both ankles in the dorsalis pedis and posterior tibial arteries (Figure 1). The blood pressure cuff is placed about 1 inch above the antecubital fossa for the brachial pressure and about 2 inches above the medial malleolus for the ankle pressures. A clear arterial pulse signal should be heard using the Doppler probe before inflating the blood pressure cuff. The cuff is then inflated to at least 20 mm Hg above the point where the arterial Doppler sounds disappear and then slowly deflated until the Doppler sounds reappear. The blood pressure at which the Doppler signal of the arterial pulse reappears is the systolic pressure for that vessel.

The ankle-brachial index is calculated by dividing the higher of the two ankle systolic blood pressures in each leg by the higher of the two brachial systolic blood pressures. The higher of the two brachial pressures is used as the denominator to account for the possibility of subclavian artery stenosis, which can decrease the blood pressure in the upper extremity. The ankle-brachial index is calculated for each leg, and the lower value is the patient’s overall ankle-brachial index. An abnormal value in either leg indicates peripheral artery disease.

While other ways of calculating the ankle-brachial index have been proposed, such as averaging the two pressures at each ankle or reporting the lower of the two ankle pressures, these methods are not standard for use in clinical practice.

Similarly, the use of oscillometric blood pressure devices has been proposed, which would eliminate the need for a Doppler device and personnel trained in its use. However, results of validation studies of oscillometric measurement of the ankle-brachial index have been inconsistent, likely because the devices were designed for measuring blood pressure in nonobstructed arms, not the legs, and especially not diseased legs.^21–25 In general, oscillometric devices tend to overestimate ankle pressure, giving a falsely high ankle-brachial index in patients with moderate to severe peripheral artery disease.²¹ Their utility in screening for peripheral artery disease has not been evaluated in broad, population-based studies. Efforts to develop and validate new oscillometric devices for diagnosing peripheral artery disease are ongoing.

INTERPRETING THE ANKLE-BRACHIAL INDEX

Diagnostic criteria for the ankle-brachial index were standardized in 2011 (Table 1).²⁶ Most healthy adults have a value greater than 1.0. A value of less than 0.91 is consistent with significant peripheral artery disease, and a value lower than 0.40 at rest generally indicates severe disease. A value between 0.91 and 0.99 is borderline abnormal and does not rule out peripheral artery disease. A value greater than 1.40 reflects noncompressibility of the leg arteries and is not diagnostic (see below).

The ankle-brachial index after exercise. In patients strongly suspected of having peripheral artery disease but who have a normal ankle-brachial index at rest, and especially if the resting value is borderline (ie, 0.91–0.99), the measurement should be repeated after exercise, the better to detect “mild” peripheral artery disease.¹⁵ With exercise, increased flow across a fixed stenosis leads to a significant fall in ankle pressure and a lower ankle-brachial index. In one study,²⁷ the ankle-brachial index fell below 0.9 after exercise in 31% of outpatients with symptoms who had initially tested normal.

The exercise is optimally done on a motorized treadmill set at an incline. A number of exercise protocols are in use; at our institution, we use a fixed workload protocol. The ankle-brachial index and ankle pulse-volume recordings are recorded on both sides at rest, after which the patient generally walks for 5 minutes at a 12% grade at 2.0 mph or until symptoms force the patient to stop. The advantage of treadmill testing is the ability to assess functional capacity by measuring the time to the onset of pain and the total walking time.

Alternatively, active pedal plantar flexion maneuvers (heel raises) or corridor walking to the point at which limiting symptoms occur can be done if a treadmill is not available, though this is not the favored approach and does not qualify as formal exercise testing for reimbursement purposes. The patient is asked to do heel raises as high and as fast as possible for 30 seconds or until limiting pain symptoms occur. Results with this maneuver have been shown to correlate well with those of treadmill exercise testing.²⁸

Immediately after any exercise maneuver, arm and ankle pressures are remeasured and bilateral ankle-brachial indices are recalculated. A fall in ankle pressure or the ankle-brachial index after exercise (generally, a fall of more than 20%) supports the diagnosis of peripheral artery disease. If the patient develops leg symptoms during exercise while his or her ankle-brachial index falls significantly, this also supports the vasculogenic nature of the leg symptoms.

An ankle-brachial index greater than 1.40 means that the pedal arteries are stiff and cannot be compressed by the blood pressure cuff. This is considered abnormal, though not necessarily diagnostic of peripheral artery disease. Noncompressible leg arteries are common among patients with long-standing diabetes mellitus or end-stage renal disease, and also can be found in obese patients.

Because toe arteries are usually compressible even when the pedal arteries are not, a toe-brachial index can be obtained to confirm the diagnosis of peripheral artery disease in these cases. This is calculated by measuring the blood pressure in the great toe using a small digital blood pressure cuff and a Doppler probe or a plethysmographic flow sensor. The toe-brachial index is calculated by dividing the toe blood pressure by the higher of the two brachial artery pressures; a value of 0.7 or less generally indicates peripheral artery disease.

WHAT SHOULD BE DONE WITH AN ABNORMAL RESULT?

An abnormal ankle-brachial index establishes the diagnosis of peripheral artery disease, and in many cases no additional diagnostic testing is necessary.

Care of patients with peripheral artery disease has three elements:

• Cardiovascular risk factor assessment and reduction to prevent myocardial infarction, stroke, and death
• Assessment and treatment of leg symptoms to improve function and quality of life
• Foot care to prevent ulcers and amputation.

Risk factor reduction. Because they have a markedly greater risk of cardiovascular disease and death, all patients with peripheral artery disease should undergo aggressive cardiovascular risk factor modification,^26,29 including:

• Antiplatelet therapy in the form of aspirin 75–325 mg daily or clopidogrel 75 mg daily as an alternative to aspirin
• Counseling and therapy for immediate smoking cessation if the patient smokes
• Treatment of hypertension to Seventh Joint National Committee goals³⁰
• Treatment of lipids to Adult Treatment Panel III goals³¹ (generally to a goal low-density lipoprotein cholesterol of less than 100 mg/dL, and less than 70 mg/dL if possible)
• Treatment of diabetes to a goal hemoglobin A_1c of less than 7% (in the absence of contraindications).³²

Exercise and anticlaudication medication. Patients with an abnormal ankle-brachial index and intermittent claudication may benefit from a supervised exercise program, a trial of drug therapy for claudication, or both. All patients with peripheral artery disease, regardless of symptoms, should be advised to incorporate aerobic exercise (ideally, walking) into their daily routine.

Cilostazol (Pletal), a phosphodiesterase inhibitor, has been given a class IA recommendation in the American College of Cardiology/American Heart Association guidelines for the treatment of intermittent claudication. The dose is generally 100 mg by mouth twice daily.²⁹

Revascularization. Patients with an abnormal ankle-brachial index and lifestyle-limiting claudication that has failed to improve with medical therapy or a course of supervised exercise training should be referred to a vascular specialist for evaluation for revascularization (endovascular therapy or surgical bypass). ²⁹ Endovascular therapy is particularly attractive for patients with claudication and evidence of aortoiliac disease (suspected in patients with gluteal or thigh claudication, diminution of the femoral pulse, or a bruit over the femoral artery on examination and confirmed by noninvasive vascular laboratory testing).

Patients who have ischemic pain at rest, gangrene, or a nonhealing lower-extremity wound that has been present for at least 2 weeks should be referred for revascularization on an urgent basis, given the risk of impending limb loss associated with critical limb ischemia.

A detailed review of the medical, endovascular, and surgical management of peripheral artery disease can be found in a supplement to the Cleveland Clinic Journal of Medicine published in 2006³³ and in comprehensive multi-society guidelines.^26,29

THE ANKLE-BRACHIAL INDEX AS A MARKER OF RISK

Low values: Peripheral artery disease

Adapted from McKenna M, et al. The ratio of ankle and arm arterial pressure as an independent predictor of mortality. Atherosclerosis 1991; 87:119–128; with permission from Elsevier.

Peripheral artery disease, as diagnosed by a low ankle-brachial index, confers an excess risk of death from all causes in a graded fashion: ie, the more severe the disease, the lower the survival rate (Figure 2).³⁴ Because peripheral artery disease is a sign of systemic atherosclerosis and one-third to one-half of patients with peripheral artery disease have evidence of cerebrovascular or coronary artery disease,^35–37 peripheral artery disease also confers a higher risk of cardiovascular death.

The Edinburgh Artery Study,³⁸ a prospective cohort study of 1,592 randomly selected patients age 55 to 74 years, demonstrated the relationship between a low ankle-brachial index and an increased risk of cardiovascular death. Over 5 years of follow-up, compared with patients with a normal ankle-brachial index, the relative risk of cardiovascular death in symptomatic patients with a value of 0.9 or lower was 2.67 (95% confidence interval [CI] 1.34–5.29). The relative risk in patients with asymptomatic disease was between 1.74 (95% CI 1.09–2.76) and 2.08 (95% CI 1.13–3.83), depending on the level of ankle-brachial index decrement and ankle blood pressure response to hyperemia.

(Reactive hyperemia is an alternative to exercise testing. It is performed by inflating a blood pressure cuff at the thigh above the systolic pressure for 3 to 5 minutes or until the patient can no longer tolerate the inflation. Blood pressures at the ankle are remeasured after cuff release.)

Several other epidemiologic studies have established the association between low ankle-brachial index and the risk of cardiovascular death.

Heald et al³⁹ performed a meta-analysis of 44,590 patients in 11 epidemiologic studies and found that, after adjustment for age, sex, conventional cardiovascular risk factors, and prevalent cardiovascular disease, an ankle-brachial index lower than 0.9 conferred a higher risk of:

• All-cause mortality (pooled risk ratio [RR] 1.60, 95% CI 1.32–1.95)
• Cardiovascular mortality (pooled RR 1.96, 95% CI 1.46–2.64)
• Coronary heart disease (pooled RR 1.45, 95% CI 1.08–1.93)
• Stroke (pooled RR 1.35, 95% CI 1.10–1.65).

Fowkes et al,⁴⁰ in a meta-analysis of 16 population cohort studies including 48,294 patients over 480,325 person-years of follow-up, found that a low ankle-brachial index predicted cardiovascular events and death even after adjusting for the Framingham risk score, Hazard ratios for cardiovascular death were:

• 2.92 (95% CI 2.31–3.70) in men
• 2.97 (95% CI 2.02–4.35) in women.

Hazard ratios for death from any cause were:

• 2.34 (95% CI 1.97–2.78) in men
• 2.35 (95% CI 1.76–3.13) in women.

Adding the ankle-brachial index to the Framingham risk score resulted in reclassification of risk category in approximately 19% of men and 36% of women.⁴⁰

Adapted from Diehm C, et al. Mortality and vascular morbidity in older adults with asymptomatic versus symptomatic peripheral artery disease. Circulation 2009; 120:2053–2061; with permission of Lippincott Williams & Wilkins.

The German Epidemiological Trial on Ankle Brachial Index (getABI) screened 6,880 patients 65 years of age and found an abnormal ankle-brachial index in 20.9% of them.⁴¹ In more than 5 years of follow-up, a value of less than 0.90 was associated with a higher rate of cardiovascular events and death from any cause in patients with both symptomatic and asymptomatic peripheral artery disease (Figure 3).⁴¹

In addition, the lower the ankle-brachial index, the greater the rate of death or severe cardiovascular events. An index between 0.7 and 0.9 was associated with a statistically significant twofold increase (adjusted hazard ratio 2.03), and a value lower than 0.5 was associated with a nearly fivefold increase (hazard ratio 4.65) in the risk of events compared with the group of patients with normal values.⁴¹

Abnormal results after exercise

Exercise testing may increase the sensitivity of the ankle-brachial index to detect peripheral artery disease in patients with normal resting values and especially in patients with borderline values. As such, abnormal exercise values have also been associated with an increased risk of death due to any cause and of cardiovascular death.

In a prospective cohort study of 3,209 patients with suspected or known peripheral artery disease referred to a vascular surgery clinic in the Netherlands, patients with lower postexercise values had a higher rate of overall and cardiac death (hazard ratio per 10% lower value 1.16 [95% CI 1.13–1.18] and 1.10 [95% CI 1.09–1.13], respectively).⁴²

Sheikh et al⁴³ reported similar findings in patients with normal resting ankle-brachial indices at Cleveland Clinic. In this study, an abnormal postexercise ankle-brachial index (defined as < 0.85) was associated with a hazard ratio of 1.67 for all-cause mortality compared with a normal postexercise value among individuals with no history of cardiovascular events.

High values: Noncompressible vessels

While the relationship between low values and increased mortality and cardiovascular risk is well accepted, there have been conflicting reports regarding high values (> 1.4) and adverse outcomes.^44,45

Adapted with permission from Resnick HE, et al. Relationship of high and low ankle brachial index to all-cause and cardiovascular disease mortality: the Strong Heart Study. Circulation 2004; 109:733–739.

The Strong Heart Study⁴⁴ was a population-based study in 4,393 Native Americans followed for more than 8 years for the rate of all-cause and cardiovascular mortality. Most (n = 3,773) of the cohort had a normal ankle-brachial index (≥ 0.9 and ≤ 1.4); 4.9% (n = 216) had a low value (< 0.9); and 9.2% (n = 404) had a high value (> 1.4 or noncompressible). Relative risk ratios for all-cause mortality were 1.69 (95% CI 1.34–2.14) for low values and 1.77 (95% CI 1.48–2.13) for high values compared with those with normal values. Low and high ankle-brachial indices also conferred a risk of cardiovascular death, with relative risk ratios of 2.52 (95% CI 1.74–3.64) and 2.09 (95% CI 1.49–2.94), respectively. There was a U-shaped relationship between the ankle-brachial index and the mortality rate (Figure 4).⁴⁴

The Atherosclerosis Risk in Communities (ARIC) study⁴⁵ had different findings. In 14,777 participants followed for a mean of 12.2 years, the cardiovascular disease event rates of patients whose ankle-brachial index-was categorized as high (> 1.3, > 1.4, or > 1.5) were similar to those of patients with a normal value (between 0.9 and 1.3).

Differences in event rates between the two studies may be due to a higher prevalence of values greater than 1.4 in the Strong Heart Study cohort as well as to a higher prevalence of concomitant risk factors (diabetes, older age, hypertension, lipid abnormality) in the high ankle-brachial index group in the Strong Heart Study compared with the ARIC study.

DIFFERING RECOMMENDATIONS

The ankle-brachial index can be used to screen for asymptomatic peripheral artery disease. It can also be used to confirm the diagnosis in patients with symptoms such as intermittent claudication, ischemic pain at rest, or lower extremity ulcers or in patients with signs such as abnormal pulses, bruits, or lower-extremity skin changes. It is also used to reassess the severity of known peripheral artery disease and as a part of a routine surveillance program to assess the patency of bypass grafts and endovascular stents after revascularization procedures.

The complication of peripheral artery disease that patients dread the most is limb loss, but of greater clinical consequence are the alarming rates of cardiovascular events and death in these patients. Epidemiologic studies have shown that fewer than 5% of patients age 55 or older with claudication or asymptomatic peripheral artery disease experience major amputation over a 5-year follow-up period, but 20% of these patients will have a stroke or myocardial infarction and 15% to 30% will die. Of those who die, 75% die of a coronary or cerebrovascular cause.³⁶ Because of the markedly increased risk of death or cardiovascular morbidity in patients with peripheral artery disease, many have advocated screening patients at high risk using the ankle-brachial index. However, there have been conflicting recommendations from national societies and agencies.^29,46–48

The United States Preventive Services Task Force (USPSTF) updated its 1996 recommendations on screening for peripheral artery disease in 2005 and recommended against routinely screening for it, giving the practice a “D” recommendation (not recommended). Specifically, it stated that it found “fair evidence that screening asymptomatic adults with the ankle brachial index could lead to some small degree of harm, including false-positive results and unnecessary work-ups,”⁴⁶ and concluded that “for asymptomatic adults, harms of routine screening for [peripheral artery disease] exceed benefits.”⁴⁶

This negative recommendation was intensely debated among vascular specialty groups, and a rebuttal was published in 2006.⁴⁹ The major area of contention was the task force’s assumption that decreased disease-specific morbidity (especially limb loss) is the most important outcome to be prevented by screening for asymptomatic peripheral artery disease, rather than adverse cardiovascular events. The USPSTF has announced plans for an update on screening for peripheral artery disease, anticipated for 2013.⁵⁰

The American College of Cardiology/American Heart Association task force in 2005 recommended that a history of walking impairment, intermittent claudication, ischemic rest pain, or nonhealing wounds be solicited as part of a standard review of systems for adults age 70 and older or adults age 50 and older who have risk factors for atherosclerosis (class IC recommendation—based only on a consensus opinion of experts, case studies, or standard of care).²⁹ In contrast to the USPSTF recommendations, the joint guidelines further recommended that patients with asymptomatic lower-extremity peripheral artery disease be identified by physical examination, ankle-brachial index, or both, to prevent myocardial infarction, stroke, or death (class IC).²⁹ Patients at risk for lower-extremity peripheral artery disease for whom ankle-brachial index measurement is recommended include those with exertional leg symptoms, those with nonhealing ulcers, those age 70 and older, and those age 50 and older who have a history of moking or diabetes.

The American Diabetes Association and the second Inter-Society Consensus for the Management of Peripheral Arterial Disease (TASC II) issued similar recommendations.⁴⁸

In 2011, the American College of Cardiology/American Heart Association task force issued a focused update to its 2005 guidelines, broadening the recommendation for testing to include patients age 65 and older on the basis of the getABI study, as well as maintaining the recommendation for testing for those age 50 and older with a history of smoking or diabetes (class IB recommendation).^26,41

The task force’s Guideline for the Assessment of Cardiovascular Risk in Asymptomatic Adults says that measuring the ankle-brachial index is reasonable for cardiovascular risk assessment in asymptomatic adults at intermediate risk (class IIA—conflicting evidence or divergence of opinion, from multiple randomized clinical trials).⁵¹ Also recommended as risk stratification tools for this patient population are measurement of carotid intima-media thickness and measurement of coronary artery calcium (both class IIA recommendations).

Unlike these tests, however, the ankle-brachial index does not require highly trained technical and medical personnel to perform and interpret. In addition, there is no risk of radiation exposure as is the case in coronary calcium measurement. It is a simpler, lower-cost, and more widely available tool for cardiovascular risk assessment.

LIMITATIONS TO ANKLE-BRACHIAL SCREENING IN PRACTICE

Although this test is relatively simple and noninvasive, it is not widely performed in primary care and cardiovascular medicine. In a study by Mohler and colleagues,⁵² the most common barriers to its use among primary care providers were the time required to perform it, lack of reimbursement for it, and limited staff availability. Currently, third-party payers do not generally reimburse for an ankle-brachial index examination performed to screen a patient who is asymptomatic but at risk for peripheral artery disease. Unfortunately, this has limited the widespread adoption of a program to detect peripheral artery disease in patients at risk.

Despite these limitations, the ankle-brachial index is an invaluable tool to both screen for peripheral artery disease in the appropriate at-risk patient populations and to diagnose it in patients who present with lower extremity symptoms. There are few diagnostic tests available today that provide such a high degree of diagnostic accuracy with as much prognostic information as the ankle-brachial index and with such little expense and risk to the patient.

In this article, we seek to convince you to measure the ankle-brachial index for any patient you suspect may have peripheral artery disease. This would include patients who are elderly, who smoke, or who have diabetes, regardless of whether or not they have symptoms. The ankle-brachial index is a simple test that involves taking the blood pressure in all four limbs using a hand-held Doppler device and then dividing the leg systolic pressure by the arm systolic pressure.

This simple test is both sensitive and specific for peripheral artery disease. It also gives a good assessment of cardiovascular risk. The downside: you or a member of your staff spends a few minutes doing it. Also, for patients without leg symptoms or abnormal findings on physical examination, you may not be paid for doing it.

Despite these limitations, the ankle-brachial index is a powerful clinical tool that deserves to be performed more often in primary care.

PERIPHERAL ARTERY DISEASE IS COMMON AND SERIOUS

Peripheral artery disease is important to detect, as it is common, it has serious consequences, and effective treatments are available. However, many patients with the disease do not have typical symptoms.

Peripheral artery disease affects up to 29% of people over age 70, depending on the population sampled.^1,2 Its classic symptom is intermittent claudication, ie, leg pain with walking that improves with rest. However, most patients do not have intermittent claudication; they have atypical leg symptoms or no symptoms at all.^2,3 While the risk factors for peripheral artery disease are similar to those for coronary artery disease, the factors most strongly associated with peripheral artery disease are older age, tobacco smoking, and diabetes mellitus.⁴ Blacks are twice as likely to have it compared with whites, even after adjusting for other cardiovascular risk factors.⁵

Untreated peripheral artery disease may have serious consequences, such as amputation, impaired functional capacity, poor quality of life, and depression.^3,6,7 In addition, it is a strong marker of atherosclerotic burden and cardiovascular risk and has been recognized as a coronary risk equivalent. Patients with peripheral artery disease are at higher risk of death, myocardial infarction, stroke, and hospitalization, with event rates as high as 21% per year.⁸

Fortunately, simple therapies have been shown to prevent adverse cardiovascular events in peripheral artery disease, including antiplatelet drugs, statins, and angiotensin-converting enzyme inhibitors.^9–11

THE ANKLE-BRACHIAL INDEX IS SENSITIVE AND SPECIFIC

The evaluation for possible peripheral artery disease should begin with the medical history, a cardiovascular review of systems, and a focused physical examination in which one should:

• Measure the blood pressure in both arms to assess for occult subclavian stenosis
• Auscultate for bruits over the carotid, abdominal, and femoral arteries
• Palpate the pulses in the lower extremities and the abdominal aorta
• Inspect the bare legs and feet for thinning of the skin, hair loss, thickening of the nails (which are nonspecific signs), and ulceration.

However, the physical examination has limited sensitivity and specificity for diagnosing peripheral artery disease. In general, the most reliable finding is the absence of a palpable posterior tibial artery pulse, which has been reported to have a specificity of 71% and a sensitivity of 91% for peripheral artery disease.¹²

The ankle-brachial index is the first-line test for both screening for peripheral artery disease and for diagnosing it. It is inexpensive and noninvasive to obtain and has a high sensitivity (79% to 95%) and specificity (95% to 96%) compared with angiography as the gold standard.^13–18 It can be measured easily in the office, and every practitioner who cares for patients at risk of cardiovascular disease can be trained to measure it competently.

HOW TO MEASURE THE ANKLE-BRACHIAL INDEX

The ankle-brachial index is the ratio of the systolic pressure in the ankle to the systolic pressure in the arm. In healthy people, this ratio is typically greater than 1.0 or 1.1.

You can measure the ankle-brachial index in the office with a blood pressure cuff, sphygmomanometer, and handheld Doppler device. Alternatively, it can be measured in a noninvasive vascular laboratory as part of a more detailed examination that allows for assessment of blood pressures and waveforms (Doppler or pulse-volume recordings) at multiple segments along the limb. These more detailed vascular studies are generally reserved for patients with confirmed peripheral artery disease to locate the level and extent of blockage or for patients in whom lower-extremity revascularization is contemplated.

The use of a stethoscope to measure blood pressures for the ankle-brachial index has been studied in a few small series,^19,20 but is thought to be less accurate than Doppler, especially in the setting of significant arterial occlusive disease. Because of this, it is recommended and assumed that a Doppler device be used to measure all blood pressures for the ankle-brachial index.

Information based on 2011 Writing Group Members, et al. 2011 ACCF/AHA focused update of the guideline for the management of patients with peripheral artery disease. Circulation 2011; 124:2020–2045.

After the patient has been resting quietly for 5 to 10 minutes in the supine position, the systolic blood pressure is measured in both arms and in both ankles in the dorsalis pedis and posterior tibial arteries (Figure 1). The blood pressure cuff is placed about 1 inch above the antecubital fossa for the brachial pressure and about 2 inches above the medial malleolus for the ankle pressures. A clear arterial pulse signal should be heard using the Doppler probe before inflating the blood pressure cuff. The cuff is then inflated to at least 20 mm Hg above the point where the arterial Doppler sounds disappear and then slowly deflated until the Doppler sounds reappear. The blood pressure at which the Doppler signal of the arterial pulse reappears is the systolic pressure for that vessel.

The ankle-brachial index is calculated by dividing the higher of the two ankle systolic blood pressures in each leg by the higher of the two brachial systolic blood pressures. The higher of the two brachial pressures is used as the denominator to account for the possibility of subclavian artery stenosis, which can decrease the blood pressure in the upper extremity. The ankle-brachial index is calculated for each leg, and the lower value is the patient’s overall ankle-brachial index. An abnormal value in either leg indicates peripheral artery disease.

While other ways of calculating the ankle-brachial index have been proposed, such as averaging the two pressures at each ankle or reporting the lower of the two ankle pressures, these methods are not standard for use in clinical practice.

Similarly, the use of oscillometric blood pressure devices has been proposed, which would eliminate the need for a Doppler device and personnel trained in its use. However, results of validation studies of oscillometric measurement of the ankle-brachial index have been inconsistent, likely because the devices were designed for measuring blood pressure in nonobstructed arms, not the legs, and especially not diseased legs.^21–25 In general, oscillometric devices tend to overestimate ankle pressure, giving a falsely high ankle-brachial index in patients with moderate to severe peripheral artery disease.²¹ Their utility in screening for peripheral artery disease has not been evaluated in broad, population-based studies. Efforts to develop and validate new oscillometric devices for diagnosing peripheral artery disease are ongoing.

INTERPRETING THE ANKLE-BRACHIAL INDEX

Diagnostic criteria for the ankle-brachial index were standardized in 2011 (Table 1).²⁶ Most healthy adults have a value greater than 1.0. A value of less than 0.91 is consistent with significant peripheral artery disease, and a value lower than 0.40 at rest generally indicates severe disease. A value between 0.91 and 0.99 is borderline abnormal and does not rule out peripheral artery disease. A value greater than 1.40 reflects noncompressibility of the leg arteries and is not diagnostic (see below).

The ankle-brachial index after exercise. In patients strongly suspected of having peripheral artery disease but who have a normal ankle-brachial index at rest, and especially if the resting value is borderline (ie, 0.91–0.99), the measurement should be repeated after exercise, the better to detect “mild” peripheral artery disease.¹⁵ With exercise, increased flow across a fixed stenosis leads to a significant fall in ankle pressure and a lower ankle-brachial index. In one study,²⁷ the ankle-brachial index fell below 0.9 after exercise in 31% of outpatients with symptoms who had initially tested normal.

The exercise is optimally done on a motorized treadmill set at an incline. A number of exercise protocols are in use; at our institution, we use a fixed workload protocol. The ankle-brachial index and ankle pulse-volume recordings are recorded on both sides at rest, after which the patient generally walks for 5 minutes at a 12% grade at 2.0 mph or until symptoms force the patient to stop. The advantage of treadmill testing is the ability to assess functional capacity by measuring the time to the onset of pain and the total walking time.

Alternatively, active pedal plantar flexion maneuvers (heel raises) or corridor walking to the point at which limiting symptoms occur can be done if a treadmill is not available, though this is not the favored approach and does not qualify as formal exercise testing for reimbursement purposes. The patient is asked to do heel raises as high and as fast as possible for 30 seconds or until limiting pain symptoms occur. Results with this maneuver have been shown to correlate well with those of treadmill exercise testing.²⁸

Immediately after any exercise maneuver, arm and ankle pressures are remeasured and bilateral ankle-brachial indices are recalculated. A fall in ankle pressure or the ankle-brachial index after exercise (generally, a fall of more than 20%) supports the diagnosis of peripheral artery disease. If the patient develops leg symptoms during exercise while his or her ankle-brachial index falls significantly, this also supports the vasculogenic nature of the leg symptoms.

An ankle-brachial index greater than 1.40 means that the pedal arteries are stiff and cannot be compressed by the blood pressure cuff. This is considered abnormal, though not necessarily diagnostic of peripheral artery disease. Noncompressible leg arteries are common among patients with long-standing diabetes mellitus or end-stage renal disease, and also can be found in obese patients.

Because toe arteries are usually compressible even when the pedal arteries are not, a toe-brachial index can be obtained to confirm the diagnosis of peripheral artery disease in these cases. This is calculated by measuring the blood pressure in the great toe using a small digital blood pressure cuff and a Doppler probe or a plethysmographic flow sensor. The toe-brachial index is calculated by dividing the toe blood pressure by the higher of the two brachial artery pressures; a value of 0.7 or less generally indicates peripheral artery disease.

WHAT SHOULD BE DONE WITH AN ABNORMAL RESULT?

An abnormal ankle-brachial index establishes the diagnosis of peripheral artery disease, and in many cases no additional diagnostic testing is necessary.

Care of patients with peripheral artery disease has three elements:

• Cardiovascular risk factor assessment and reduction to prevent myocardial infarction, stroke, and death
• Assessment and treatment of leg symptoms to improve function and quality of life
• Foot care to prevent ulcers and amputation.

Risk factor reduction. Because they have a markedly greater risk of cardiovascular disease and death, all patients with peripheral artery disease should undergo aggressive cardiovascular risk factor modification,^26,29 including:

• Antiplatelet therapy in the form of aspirin 75–325 mg daily or clopidogrel 75 mg daily as an alternative to aspirin
• Counseling and therapy for immediate smoking cessation if the patient smokes
• Treatment of hypertension to Seventh Joint National Committee goals³⁰
• Treatment of lipids to Adult Treatment Panel III goals³¹ (generally to a goal low-density lipoprotein cholesterol of less than 100 mg/dL, and less than 70 mg/dL if possible)
• Treatment of diabetes to a goal hemoglobin A_1c of less than 7% (in the absence of contraindications).³²

Exercise and anticlaudication medication. Patients with an abnormal ankle-brachial index and intermittent claudication may benefit from a supervised exercise program, a trial of drug therapy for claudication, or both. All patients with peripheral artery disease, regardless of symptoms, should be advised to incorporate aerobic exercise (ideally, walking) into their daily routine.

Cilostazol (Pletal), a phosphodiesterase inhibitor, has been given a class IA recommendation in the American College of Cardiology/American Heart Association guidelines for the treatment of intermittent claudication. The dose is generally 100 mg by mouth twice daily.²⁹

Revascularization. Patients with an abnormal ankle-brachial index and lifestyle-limiting claudication that has failed to improve with medical therapy or a course of supervised exercise training should be referred to a vascular specialist for evaluation for revascularization (endovascular therapy or surgical bypass). ²⁹ Endovascular therapy is particularly attractive for patients with claudication and evidence of aortoiliac disease (suspected in patients with gluteal or thigh claudication, diminution of the femoral pulse, or a bruit over the femoral artery on examination and confirmed by noninvasive vascular laboratory testing).

Patients who have ischemic pain at rest, gangrene, or a nonhealing lower-extremity wound that has been present for at least 2 weeks should be referred for revascularization on an urgent basis, given the risk of impending limb loss associated with critical limb ischemia.

A detailed review of the medical, endovascular, and surgical management of peripheral artery disease can be found in a supplement to the Cleveland Clinic Journal of Medicine published in 2006³³ and in comprehensive multi-society guidelines.^26,29

THE ANKLE-BRACHIAL INDEX AS A MARKER OF RISK

Low values: Peripheral artery disease

Adapted from McKenna M, et al. The ratio of ankle and arm arterial pressure as an independent predictor of mortality. Atherosclerosis 1991; 87:119–128; with permission from Elsevier.

Peripheral artery disease, as diagnosed by a low ankle-brachial index, confers an excess risk of death from all causes in a graded fashion: ie, the more severe the disease, the lower the survival rate (Figure 2).³⁴ Because peripheral artery disease is a sign of systemic atherosclerosis and one-third to one-half of patients with peripheral artery disease have evidence of cerebrovascular or coronary artery disease,^35–37 peripheral artery disease also confers a higher risk of cardiovascular death.

The Edinburgh Artery Study,³⁸ a prospective cohort study of 1,592 randomly selected patients age 55 to 74 years, demonstrated the relationship between a low ankle-brachial index and an increased risk of cardiovascular death. Over 5 years of follow-up, compared with patients with a normal ankle-brachial index, the relative risk of cardiovascular death in symptomatic patients with a value of 0.9 or lower was 2.67 (95% confidence interval [CI] 1.34–5.29). The relative risk in patients with asymptomatic disease was between 1.74 (95% CI 1.09–2.76) and 2.08 (95% CI 1.13–3.83), depending on the level of ankle-brachial index decrement and ankle blood pressure response to hyperemia.

(Reactive hyperemia is an alternative to exercise testing. It is performed by inflating a blood pressure cuff at the thigh above the systolic pressure for 3 to 5 minutes or until the patient can no longer tolerate the inflation. Blood pressures at the ankle are remeasured after cuff release.)

Several other epidemiologic studies have established the association between low ankle-brachial index and the risk of cardiovascular death.

Heald et al³⁹ performed a meta-analysis of 44,590 patients in 11 epidemiologic studies and found that, after adjustment for age, sex, conventional cardiovascular risk factors, and prevalent cardiovascular disease, an ankle-brachial index lower than 0.9 conferred a higher risk of:

• All-cause mortality (pooled risk ratio [RR] 1.60, 95% CI 1.32–1.95)
• Cardiovascular mortality (pooled RR 1.96, 95% CI 1.46–2.64)
• Coronary heart disease (pooled RR 1.45, 95% CI 1.08–1.93)
• Stroke (pooled RR 1.35, 95% CI 1.10–1.65).

Fowkes et al,⁴⁰ in a meta-analysis of 16 population cohort studies including 48,294 patients over 480,325 person-years of follow-up, found that a low ankle-brachial index predicted cardiovascular events and death even after adjusting for the Framingham risk score, Hazard ratios for cardiovascular death were:

• 2.92 (95% CI 2.31–3.70) in men
• 2.97 (95% CI 2.02–4.35) in women.

Hazard ratios for death from any cause were:

• 2.34 (95% CI 1.97–2.78) in men
• 2.35 (95% CI 1.76–3.13) in women.

Adding the ankle-brachial index to the Framingham risk score resulted in reclassification of risk category in approximately 19% of men and 36% of women.⁴⁰

Adapted from Diehm C, et al. Mortality and vascular morbidity in older adults with asymptomatic versus symptomatic peripheral artery disease. Circulation 2009; 120:2053–2061; with permission of Lippincott Williams &amp; Wilkins.

The German Epidemiological Trial on Ankle Brachial Index (getABI) screened 6,880 patients 65 years of age and found an abnormal ankle-brachial index in 20.9% of them.⁴¹ In more than 5 years of follow-up, a value of less than 0.90 was associated with a higher rate of cardiovascular events and death from any cause in patients with both symptomatic and asymptomatic peripheral artery disease (Figure 3).⁴¹

In addition, the lower the ankle-brachial index, the greater the rate of death or severe cardiovascular events. An index between 0.7 and 0.9 was associated with a statistically significant twofold increase (adjusted hazard ratio 2.03), and a value lower than 0.5 was associated with a nearly fivefold increase (hazard ratio 4.65) in the risk of events compared with the group of patients with normal values.⁴¹

Abnormal results after exercise

Exercise testing may increase the sensitivity of the ankle-brachial index to detect peripheral artery disease in patients with normal resting values and especially in patients with borderline values. As such, abnormal exercise values have also been associated with an increased risk of death due to any cause and of cardiovascular death.

In a prospective cohort study of 3,209 patients with suspected or known peripheral artery disease referred to a vascular surgery clinic in the Netherlands, patients with lower postexercise values had a higher rate of overall and cardiac death (hazard ratio per 10% lower value 1.16 [95% CI 1.13–1.18] and 1.10 [95% CI 1.09–1.13], respectively).⁴²

Sheikh et al⁴³ reported similar findings in patients with normal resting ankle-brachial indices at Cleveland Clinic. In this study, an abnormal postexercise ankle-brachial index (defined as < 0.85) was associated with a hazard ratio of 1.67 for all-cause mortality compared with a normal postexercise value among individuals with no history of cardiovascular events.

High values: Noncompressible vessels

While the relationship between low values and increased mortality and cardiovascular risk is well accepted, there have been conflicting reports regarding high values (> 1.4) and adverse outcomes.^44,45

Adapted with permission from Resnick HE, et al. Relationship of high and low ankle brachial index to all-cause and cardiovascular disease mortality: the Strong Heart Study. Circulation 2004; 109:733–739.

The Strong Heart Study⁴⁴ was a population-based study in 4,393 Native Americans followed for more than 8 years for the rate of all-cause and cardiovascular mortality. Most (n = 3,773) of the cohort had a normal ankle-brachial index (≥ 0.9 and ≤ 1.4); 4.9% (n = 216) had a low value (< 0.9); and 9.2% (n = 404) had a high value (> 1.4 or noncompressible). Relative risk ratios for all-cause mortality were 1.69 (95% CI 1.34–2.14) for low values and 1.77 (95% CI 1.48–2.13) for high values compared with those with normal values. Low and high ankle-brachial indices also conferred a risk of cardiovascular death, with relative risk ratios of 2.52 (95% CI 1.74–3.64) and 2.09 (95% CI 1.49–2.94), respectively. There was a U-shaped relationship between the ankle-brachial index and the mortality rate (Figure 4).⁴⁴

The Atherosclerosis Risk in Communities (ARIC) study⁴⁵ had different findings. In 14,777 participants followed for a mean of 12.2 years, the cardiovascular disease event rates of patients whose ankle-brachial index-was categorized as high (> 1.3, > 1.4, or > 1.5) were similar to those of patients with a normal value (between 0.9 and 1.3).

Differences in event rates between the two studies may be due to a higher prevalence of values greater than 1.4 in the Strong Heart Study cohort as well as to a higher prevalence of concomitant risk factors (diabetes, older age, hypertension, lipid abnormality) in the high ankle-brachial index group in the Strong Heart Study compared with the ARIC study.

DIFFERING RECOMMENDATIONS

The ankle-brachial index can be used to screen for asymptomatic peripheral artery disease. It can also be used to confirm the diagnosis in patients with symptoms such as intermittent claudication, ischemic pain at rest, or lower extremity ulcers or in patients with signs such as abnormal pulses, bruits, or lower-extremity skin changes. It is also used to reassess the severity of known peripheral artery disease and as a part of a routine surveillance program to assess the patency of bypass grafts and endovascular stents after revascularization procedures.

The complication of peripheral artery disease that patients dread the most is limb loss, but of greater clinical consequence are the alarming rates of cardiovascular events and death in these patients. Epidemiologic studies have shown that fewer than 5% of patients age 55 or older with claudication or asymptomatic peripheral artery disease experience major amputation over a 5-year follow-up period, but 20% of these patients will have a stroke or myocardial infarction and 15% to 30% will die. Of those who die, 75% die of a coronary or cerebrovascular cause.³⁶ Because of the markedly increased risk of death or cardiovascular morbidity in patients with peripheral artery disease, many have advocated screening patients at high risk using the ankle-brachial index. However, there have been conflicting recommendations from national societies and agencies.^29,46–48

The United States Preventive Services Task Force (USPSTF) updated its 1996 recommendations on screening for peripheral artery disease in 2005 and recommended against routinely screening for it, giving the practice a “D” recommendation (not recommended). Specifically, it stated that it found “fair evidence that screening asymptomatic adults with the ankle brachial index could lead to some small degree of harm, including false-positive results and unnecessary work-ups,”⁴⁶ and concluded that “for asymptomatic adults, harms of routine screening for [peripheral artery disease] exceed benefits.”⁴⁶

This negative recommendation was intensely debated among vascular specialty groups, and a rebuttal was published in 2006.⁴⁹ The major area of contention was the task force’s assumption that decreased disease-specific morbidity (especially limb loss) is the most important outcome to be prevented by screening for asymptomatic peripheral artery disease, rather than adverse cardiovascular events. The USPSTF has announced plans for an update on screening for peripheral artery disease, anticipated for 2013.⁵⁰

The American College of Cardiology/American Heart Association task force in 2005 recommended that a history of walking impairment, intermittent claudication, ischemic rest pain, or nonhealing wounds be solicited as part of a standard review of systems for adults age 70 and older or adults age 50 and older who have risk factors for atherosclerosis (class IC recommendation—based only on a consensus opinion of experts, case studies, or standard of care).²⁹ In contrast to the USPSTF recommendations, the joint guidelines further recommended that patients with asymptomatic lower-extremity peripheral artery disease be identified by physical examination, ankle-brachial index, or both, to prevent myocardial infarction, stroke, or death (class IC).²⁹ Patients at risk for lower-extremity peripheral artery disease for whom ankle-brachial index measurement is recommended include those with exertional leg symptoms, those with nonhealing ulcers, those age 70 and older, and those age 50 and older who have a history of moking or diabetes.

The American Diabetes Association and the second Inter-Society Consensus for the Management of Peripheral Arterial Disease (TASC II) issued similar recommendations.⁴⁸

In 2011, the American College of Cardiology/American Heart Association task force issued a focused update to its 2005 guidelines, broadening the recommendation for testing to include patients age 65 and older on the basis of the getABI study, as well as maintaining the recommendation for testing for those age 50 and older with a history of smoking or diabetes (class IB recommendation).^26,41

The task force’s Guideline for the Assessment of Cardiovascular Risk in Asymptomatic Adults says that measuring the ankle-brachial index is reasonable for cardiovascular risk assessment in asymptomatic adults at intermediate risk (class IIA—conflicting evidence or divergence of opinion, from multiple randomized clinical trials).⁵¹ Also recommended as risk stratification tools for this patient population are measurement of carotid intima-media thickness and measurement of coronary artery calcium (both class IIA recommendations).

Unlike these tests, however, the ankle-brachial index does not require highly trained technical and medical personnel to perform and interpret. In addition, there is no risk of radiation exposure as is the case in coronary calcium measurement. It is a simpler, lower-cost, and more widely available tool for cardiovascular risk assessment.

LIMITATIONS TO ANKLE-BRACHIAL SCREENING IN PRACTICE

Although this test is relatively simple and noninvasive, it is not widely performed in primary care and cardiovascular medicine. In a study by Mohler and colleagues,⁵² the most common barriers to its use among primary care providers were the time required to perform it, lack of reimbursement for it, and limited staff availability. Currently, third-party payers do not generally reimburse for an ankle-brachial index examination performed to screen a patient who is asymptomatic but at risk for peripheral artery disease. Unfortunately, this has limited the widespread adoption of a program to detect peripheral artery disease in patients at risk.

Despite these limitations, the ankle-brachial index is an invaluable tool to both screen for peripheral artery disease in the appropriate at-risk patient populations and to diagnose it in patients who present with lower extremity symptoms. There are few diagnostic tests available today that provide such a high degree of diagnostic accuracy with as much prognostic information as the ankle-brachial index and with such little expense and risk to the patient.

In this article, we seek to convince you to measure the ankle-brachial index for any patient you suspect may have peripheral artery disease. This would include patients who are elderly, who smoke, or who have diabetes, regardless of whether or not they have symptoms. The ankle-brachial index is a simple test that involves taking the blood pressure in all four limbs using a hand-held Doppler device and then dividing the leg systolic pressure by the arm systolic pressure.

This simple test is both sensitive and specific for peripheral artery disease. It also gives a good assessment of cardiovascular risk. The downside: you or a member of your staff spends a few minutes doing it. Also, for patients without leg symptoms or abnormal findings on physical examination, you may not be paid for doing it.

Despite these limitations, the ankle-brachial index is a powerful clinical tool that deserves to be performed more often in primary care.

PERIPHERAL ARTERY DISEASE IS COMMON AND SERIOUS

Peripheral artery disease is important to detect, as it is common, it has serious consequences, and effective treatments are available. However, many patients with the disease do not have typical symptoms.

Peripheral artery disease affects up to 29% of people over age 70, depending on the population sampled.^1,2 Its classic symptom is intermittent claudication, ie, leg pain with walking that improves with rest. However, most patients do not have intermittent claudication; they have atypical leg symptoms or no symptoms at all.^2,3 While the risk factors for peripheral artery disease are similar to those for coronary artery disease, the factors most strongly associated with peripheral artery disease are older age, tobacco smoking, and diabetes mellitus.⁴ Blacks are twice as likely to have it compared with whites, even after adjusting for other cardiovascular risk factors.⁵

Untreated peripheral artery disease may have serious consequences, such as amputation, impaired functional capacity, poor quality of life, and depression.^3,6,7 In addition, it is a strong marker of atherosclerotic burden and cardiovascular risk and has been recognized as a coronary risk equivalent. Patients with peripheral artery disease are at higher risk of death, myocardial infarction, stroke, and hospitalization, with event rates as high as 21% per year.⁸

Fortunately, simple therapies have been shown to prevent adverse cardiovascular events in peripheral artery disease, including antiplatelet drugs, statins, and angiotensin-converting enzyme inhibitors.^9–11

THE ANKLE-BRACHIAL INDEX IS SENSITIVE AND SPECIFIC

The evaluation for possible peripheral artery disease should begin with the medical history, a cardiovascular review of systems, and a focused physical examination in which one should:

• Measure the blood pressure in both arms to assess for occult subclavian stenosis
• Auscultate for bruits over the carotid, abdominal, and femoral arteries
• Palpate the pulses in the lower extremities and the abdominal aorta
• Inspect the bare legs and feet for thinning of the skin, hair loss, thickening of the nails (which are nonspecific signs), and ulceration.

However, the physical examination has limited sensitivity and specificity for diagnosing peripheral artery disease. In general, the most reliable finding is the absence of a palpable posterior tibial artery pulse, which has been reported to have a specificity of 71% and a sensitivity of 91% for peripheral artery disease.¹²

The ankle-brachial index is the first-line test for both screening for peripheral artery disease and for diagnosing it. It is inexpensive and noninvasive to obtain and has a high sensitivity (79% to 95%) and specificity (95% to 96%) compared with angiography as the gold standard.^13–18 It can be measured easily in the office, and every practitioner who cares for patients at risk of cardiovascular disease can be trained to measure it competently.

HOW TO MEASURE THE ANKLE-BRACHIAL INDEX

The ankle-brachial index is the ratio of the systolic pressure in the ankle to the systolic pressure in the arm. In healthy people, this ratio is typically greater than 1.0 or 1.1.

You can measure the ankle-brachial index in the office with a blood pressure cuff, sphygmomanometer, and handheld Doppler device. Alternatively, it can be measured in a noninvasive vascular laboratory as part of a more detailed examination that allows for assessment of blood pressures and waveforms (Doppler or pulse-volume recordings) at multiple segments along the limb. These more detailed vascular studies are generally reserved for patients with confirmed peripheral artery disease to locate the level and extent of blockage or for patients in whom lower-extremity revascularization is contemplated.

The use of a stethoscope to measure blood pressures for the ankle-brachial index has been studied in a few small series,^19,20 but is thought to be less accurate than Doppler, especially in the setting of significant arterial occlusive disease. Because of this, it is recommended and assumed that a Doppler device be used to measure all blood pressures for the ankle-brachial index.

Information based on 2011 Writing Group Members, et al. 2011 ACCF/AHA focused update of the guideline for the management of patients with peripheral artery disease. Circulation 2011; 124:2020–2045.

After the patient has been resting quietly for 5 to 10 minutes in the supine position, the systolic blood pressure is measured in both arms and in both ankles in the dorsalis pedis and posterior tibial arteries (Figure 1). The blood pressure cuff is placed about 1 inch above the antecubital fossa for the brachial pressure and about 2 inches above the medial malleolus for the ankle pressures. A clear arterial pulse signal should be heard using the Doppler probe before inflating the blood pressure cuff. The cuff is then inflated to at least 20 mm Hg above the point where the arterial Doppler sounds disappear and then slowly deflated until the Doppler sounds reappear. The blood pressure at which the Doppler signal of the arterial pulse reappears is the systolic pressure for that vessel.

The ankle-brachial index is calculated by dividing the higher of the two ankle systolic blood pressures in each leg by the higher of the two brachial systolic blood pressures. The higher of the two brachial pressures is used as the denominator to account for the possibility of subclavian artery stenosis, which can decrease the blood pressure in the upper extremity. The ankle-brachial index is calculated for each leg, and the lower value is the patient’s overall ankle-brachial index. An abnormal value in either leg indicates peripheral artery disease.

While other ways of calculating the ankle-brachial index have been proposed, such as averaging the two pressures at each ankle or reporting the lower of the two ankle pressures, these methods are not standard for use in clinical practice.

Similarly, the use of oscillometric blood pressure devices has been proposed, which would eliminate the need for a Doppler device and personnel trained in its use. However, results of validation studies of oscillometric measurement of the ankle-brachial index have been inconsistent, likely because the devices were designed for measuring blood pressure in nonobstructed arms, not the legs, and especially not diseased legs.^21–25 In general, oscillometric devices tend to overestimate ankle pressure, giving a falsely high ankle-brachial index in patients with moderate to severe peripheral artery disease.²¹ Their utility in screening for peripheral artery disease has not been evaluated in broad, population-based studies. Efforts to develop and validate new oscillometric devices for diagnosing peripheral artery disease are ongoing.

INTERPRETING THE ANKLE-BRACHIAL INDEX

Diagnostic criteria for the ankle-brachial index were standardized in 2011 (Table 1).²⁶ Most healthy adults have a value greater than 1.0. A value of less than 0.91 is consistent with significant peripheral artery disease, and a value lower than 0.40 at rest generally indicates severe disease. A value between 0.91 and 0.99 is borderline abnormal and does not rule out peripheral artery disease. A value greater than 1.40 reflects noncompressibility of the leg arteries and is not diagnostic (see below).

The ankle-brachial index after exercise. In patients strongly suspected of having peripheral artery disease but who have a normal ankle-brachial index at rest, and especially if the resting value is borderline (ie, 0.91–0.99), the measurement should be repeated after exercise, the better to detect “mild” peripheral artery disease.¹⁵ With exercise, increased flow across a fixed stenosis leads to a significant fall in ankle pressure and a lower ankle-brachial index. In one study,²⁷ the ankle-brachial index fell below 0.9 after exercise in 31% of outpatients with symptoms who had initially tested normal.

The exercise is optimally done on a motorized treadmill set at an incline. A number of exercise protocols are in use; at our institution, we use a fixed workload protocol. The ankle-brachial index and ankle pulse-volume recordings are recorded on both sides at rest, after which the patient generally walks for 5 minutes at a 12% grade at 2.0 mph or until symptoms force the patient to stop. The advantage of treadmill testing is the ability to assess functional capacity by measuring the time to the onset of pain and the total walking time.

Alternatively, active pedal plantar flexion maneuvers (heel raises) or corridor walking to the point at which limiting symptoms occur can be done if a treadmill is not available, though this is not the favored approach and does not qualify as formal exercise testing for reimbursement purposes. The patient is asked to do heel raises as high and as fast as possible for 30 seconds or until limiting pain symptoms occur. Results with this maneuver have been shown to correlate well with those of treadmill exercise testing.²⁸

Immediately after any exercise maneuver, arm and ankle pressures are remeasured and bilateral ankle-brachial indices are recalculated. A fall in ankle pressure or the ankle-brachial index after exercise (generally, a fall of more than 20%) supports the diagnosis of peripheral artery disease. If the patient develops leg symptoms during exercise while his or her ankle-brachial index falls significantly, this also supports the vasculogenic nature of the leg symptoms.

An ankle-brachial index greater than 1.40 means that the pedal arteries are stiff and cannot be compressed by the blood pressure cuff. This is considered abnormal, though not necessarily diagnostic of peripheral artery disease. Noncompressible leg arteries are common among patients with long-standing diabetes mellitus or end-stage renal disease, and also can be found in obese patients.

Because toe arteries are usually compressible even when the pedal arteries are not, a toe-brachial index can be obtained to confirm the diagnosis of peripheral artery disease in these cases. This is calculated by measuring the blood pressure in the great toe using a small digital blood pressure cuff and a Doppler probe or a plethysmographic flow sensor. The toe-brachial index is calculated by dividing the toe blood pressure by the higher of the two brachial artery pressures; a value of 0.7 or less generally indicates peripheral artery disease.

WHAT SHOULD BE DONE WITH AN ABNORMAL RESULT?

An abnormal ankle-brachial index establishes the diagnosis of peripheral artery disease, and in many cases no additional diagnostic testing is necessary.

Care of patients with peripheral artery disease has three elements:

• Cardiovascular risk factor assessment and reduction to prevent myocardial infarction, stroke, and death
• Assessment and treatment of leg symptoms to improve function and quality of life
• Foot care to prevent ulcers and amputation.

Risk factor reduction. Because they have a markedly greater risk of cardiovascular disease and death, all patients with peripheral artery disease should undergo aggressive cardiovascular risk factor modification,^26,29 including:

• Antiplatelet therapy in the form of aspirin 75–325 mg daily or clopidogrel 75 mg daily as an alternative to aspirin
• Counseling and therapy for immediate smoking cessation if the patient smokes
• Treatment of hypertension to Seventh Joint National Committee goals³⁰
• Treatment of lipids to Adult Treatment Panel III goals³¹ (generally to a goal low-density lipoprotein cholesterol of less than 100 mg/dL, and less than 70 mg/dL if possible)
• Treatment of diabetes to a goal hemoglobin A_1c of less than 7% (in the absence of contraindications).³²

Exercise and anticlaudication medication. Patients with an abnormal ankle-brachial index and intermittent claudication may benefit from a supervised exercise program, a trial of drug therapy for claudication, or both. All patients with peripheral artery disease, regardless of symptoms, should be advised to incorporate aerobic exercise (ideally, walking) into their daily routine.

Cilostazol (Pletal), a phosphodiesterase inhibitor, has been given a class IA recommendation in the American College of Cardiology/American Heart Association guidelines for the treatment of intermittent claudication. The dose is generally 100 mg by mouth twice daily.²⁹

Revascularization. Patients with an abnormal ankle-brachial index and lifestyle-limiting claudication that has failed to improve with medical therapy or a course of supervised exercise training should be referred to a vascular specialist for evaluation for revascularization (endovascular therapy or surgical bypass). ²⁹ Endovascular therapy is particularly attractive for patients with claudication and evidence of aortoiliac disease (suspected in patients with gluteal or thigh claudication, diminution of the femoral pulse, or a bruit over the femoral artery on examination and confirmed by noninvasive vascular laboratory testing).

Patients who have ischemic pain at rest, gangrene, or a nonhealing lower-extremity wound that has been present for at least 2 weeks should be referred for revascularization on an urgent basis, given the risk of impending limb loss associated with critical limb ischemia.

A detailed review of the medical, endovascular, and surgical management of peripheral artery disease can be found in a supplement to the Cleveland Clinic Journal of Medicine published in 2006³³ and in comprehensive multi-society guidelines.^26,29

THE ANKLE-BRACHIAL INDEX AS A MARKER OF RISK

Low values: Peripheral artery disease

Adapted from McKenna M, et al. The ratio of ankle and arm arterial pressure as an independent predictor of mortality. Atherosclerosis 1991; 87:119–128; with permission from Elsevier.

Peripheral artery disease, as diagnosed by a low ankle-brachial index, confers an excess risk of death from all causes in a graded fashion: ie, the more severe the disease, the lower the survival rate (Figure 2).³⁴ Because peripheral artery disease is a sign of systemic atherosclerosis and one-third to one-half of patients with peripheral artery disease have evidence of cerebrovascular or coronary artery disease,^35–37 peripheral artery disease also confers a higher risk of cardiovascular death.

The Edinburgh Artery Study,³⁸ a prospective cohort study of 1,592 randomly selected patients age 55 to 74 years, demonstrated the relationship between a low ankle-brachial index and an increased risk of cardiovascular death. Over 5 years of follow-up, compared with patients with a normal ankle-brachial index, the relative risk of cardiovascular death in symptomatic patients with a value of 0.9 or lower was 2.67 (95% confidence interval [CI] 1.34–5.29). The relative risk in patients with asymptomatic disease was between 1.74 (95% CI 1.09–2.76) and 2.08 (95% CI 1.13–3.83), depending on the level of ankle-brachial index decrement and ankle blood pressure response to hyperemia.

(Reactive hyperemia is an alternative to exercise testing. It is performed by inflating a blood pressure cuff at the thigh above the systolic pressure for 3 to 5 minutes or until the patient can no longer tolerate the inflation. Blood pressures at the ankle are remeasured after cuff release.)

Several other epidemiologic studies have established the association between low ankle-brachial index and the risk of cardiovascular death.

Heald et al³⁹ performed a meta-analysis of 44,590 patients in 11 epidemiologic studies and found that, after adjustment for age, sex, conventional cardiovascular risk factors, and prevalent cardiovascular disease, an ankle-brachial index lower than 0.9 conferred a higher risk of:

• All-cause mortality (pooled risk ratio [RR] 1.60, 95% CI 1.32–1.95)
• Cardiovascular mortality (pooled RR 1.96, 95% CI 1.46–2.64)
• Coronary heart disease (pooled RR 1.45, 95% CI 1.08–1.93)
• Stroke (pooled RR 1.35, 95% CI 1.10–1.65).

Fowkes et al,⁴⁰ in a meta-analysis of 16 population cohort studies including 48,294 patients over 480,325 person-years of follow-up, found that a low ankle-brachial index predicted cardiovascular events and death even after adjusting for the Framingham risk score, Hazard ratios for cardiovascular death were:

• 2.92 (95% CI 2.31–3.70) in men
• 2.97 (95% CI 2.02–4.35) in women.

Hazard ratios for death from any cause were:

• 2.34 (95% CI 1.97–2.78) in men
• 2.35 (95% CI 1.76–3.13) in women.

Adding the ankle-brachial index to the Framingham risk score resulted in reclassification of risk category in approximately 19% of men and 36% of women.⁴⁰

Adapted from Diehm C, et al. Mortality and vascular morbidity in older adults with asymptomatic versus symptomatic peripheral artery disease. Circulation 2009; 120:2053–2061; with permission of Lippincott Williams &amp; Wilkins.

The German Epidemiological Trial on Ankle Brachial Index (getABI) screened 6,880 patients 65 years of age and found an abnormal ankle-brachial index in 20.9% of them.⁴¹ In more than 5 years of follow-up, a value of less than 0.90 was associated with a higher rate of cardiovascular events and death from any cause in patients with both symptomatic and asymptomatic peripheral artery disease (Figure 3).⁴¹

In addition, the lower the ankle-brachial index, the greater the rate of death or severe cardiovascular events. An index between 0.7 and 0.9 was associated with a statistically significant twofold increase (adjusted hazard ratio 2.03), and a value lower than 0.5 was associated with a nearly fivefold increase (hazard ratio 4.65) in the risk of events compared with the group of patients with normal values.⁴¹

Abnormal results after exercise

Exercise testing may increase the sensitivity of the ankle-brachial index to detect peripheral artery disease in patients with normal resting values and especially in patients with borderline values. As such, abnormal exercise values have also been associated with an increased risk of death due to any cause and of cardiovascular death.

In a prospective cohort study of 3,209 patients with suspected or known peripheral artery disease referred to a vascular surgery clinic in the Netherlands, patients with lower postexercise values had a higher rate of overall and cardiac death (hazard ratio per 10% lower value 1.16 [95% CI 1.13–1.18] and 1.10 [95% CI 1.09–1.13], respectively).⁴²

Sheikh et al⁴³ reported similar findings in patients with normal resting ankle-brachial indices at Cleveland Clinic. In this study, an abnormal postexercise ankle-brachial index (defined as < 0.85) was associated with a hazard ratio of 1.67 for all-cause mortality compared with a normal postexercise value among individuals with no history of cardiovascular events.

High values: Noncompressible vessels

While the relationship between low values and increased mortality and cardiovascular risk is well accepted, there have been conflicting reports regarding high values (> 1.4) and adverse outcomes.^44,45

Adapted with permission from Resnick HE, et al. Relationship of high and low ankle brachial index to all-cause and cardiovascular disease mortality: the Strong Heart Study. Circulation 2004; 109:733–739.

The Strong Heart Study⁴⁴ was a population-based study in 4,393 Native Americans followed for more than 8 years for the rate of all-cause and cardiovascular mortality. Most (n = 3,773) of the cohort had a normal ankle-brachial index (≥ 0.9 and ≤ 1.4); 4.9% (n = 216) had a low value (< 0.9); and 9.2% (n = 404) had a high value (> 1.4 or noncompressible). Relative risk ratios for all-cause mortality were 1.69 (95% CI 1.34–2.14) for low values and 1.77 (95% CI 1.48–2.13) for high values compared with those with normal values. Low and high ankle-brachial indices also conferred a risk of cardiovascular death, with relative risk ratios of 2.52 (95% CI 1.74–3.64) and 2.09 (95% CI 1.49–2.94), respectively. There was a U-shaped relationship between the ankle-brachial index and the mortality rate (Figure 4).⁴⁴

The Atherosclerosis Risk in Communities (ARIC) study⁴⁵ had different findings. In 14,777 participants followed for a mean of 12.2 years, the cardiovascular disease event rates of patients whose ankle-brachial index-was categorized as high (> 1.3, > 1.4, or > 1.5) were similar to those of patients with a normal value (between 0.9 and 1.3).

Differences in event rates between the two studies may be due to a higher prevalence of values greater than 1.4 in the Strong Heart Study cohort as well as to a higher prevalence of concomitant risk factors (diabetes, older age, hypertension, lipid abnormality) in the high ankle-brachial index group in the Strong Heart Study compared with the ARIC study.

DIFFERING RECOMMENDATIONS

The ankle-brachial index can be used to screen for asymptomatic peripheral artery disease. It can also be used to confirm the diagnosis in patients with symptoms such as intermittent claudication, ischemic pain at rest, or lower extremity ulcers or in patients with signs such as abnormal pulses, bruits, or lower-extremity skin changes. It is also used to reassess the severity of known peripheral artery disease and as a part of a routine surveillance program to assess the patency of bypass grafts and endovascular stents after revascularization procedures.

The complication of peripheral artery disease that patients dread the most is limb loss, but of greater clinical consequence are the alarming rates of cardiovascular events and death in these patients. Epidemiologic studies have shown that fewer than 5% of patients age 55 or older with claudication or asymptomatic peripheral artery disease experience major amputation over a 5-year follow-up period, but 20% of these patients will have a stroke or myocardial infarction and 15% to 30% will die. Of those who die, 75% die of a coronary or cerebrovascular cause.³⁶ Because of the markedly increased risk of death or cardiovascular morbidity in patients with peripheral artery disease, many have advocated screening patients at high risk using the ankle-brachial index. However, there have been conflicting recommendations from national societies and agencies.^29,46–48

The United States Preventive Services Task Force (USPSTF) updated its 1996 recommendations on screening for peripheral artery disease in 2005 and recommended against routinely screening for it, giving the practice a “D” recommendation (not recommended). Specifically, it stated that it found “fair evidence that screening asymptomatic adults with the ankle brachial index could lead to some small degree of harm, including false-positive results and unnecessary work-ups,”⁴⁶ and concluded that “for asymptomatic adults, harms of routine screening for [peripheral artery disease] exceed benefits.”⁴⁶

This negative recommendation was intensely debated among vascular specialty groups, and a rebuttal was published in 2006.⁴⁹ The major area of contention was the task force’s assumption that decreased disease-specific morbidity (especially limb loss) is the most important outcome to be prevented by screening for asymptomatic peripheral artery disease, rather than adverse cardiovascular events. The USPSTF has announced plans for an update on screening for peripheral artery disease, anticipated for 2013.⁵⁰

The American College of Cardiology/American Heart Association task force in 2005 recommended that a history of walking impairment, intermittent claudication, ischemic rest pain, or nonhealing wounds be solicited as part of a standard review of systems for adults age 70 and older or adults age 50 and older who have risk factors for atherosclerosis (class IC recommendation—based only on a consensus opinion of experts, case studies, or standard of care).²⁹ In contrast to the USPSTF recommendations, the joint guidelines further recommended that patients with asymptomatic lower-extremity peripheral artery disease be identified by physical examination, ankle-brachial index, or both, to prevent myocardial infarction, stroke, or death (class IC).²⁹ Patients at risk for lower-extremity peripheral artery disease for whom ankle-brachial index measurement is recommended include those with exertional leg symptoms, those with nonhealing ulcers, those age 70 and older, and those age 50 and older who have a history of moking or diabetes.

The American Diabetes Association and the second Inter-Society Consensus for the Management of Peripheral Arterial Disease (TASC II) issued similar recommendations.⁴⁸

In 2011, the American College of Cardiology/American Heart Association task force issued a focused update to its 2005 guidelines, broadening the recommendation for testing to include patients age 65 and older on the basis of the getABI study, as well as maintaining the recommendation for testing for those age 50 and older with a history of smoking or diabetes (class IB recommendation).^26,41

The task force’s Guideline for the Assessment of Cardiovascular Risk in Asymptomatic Adults says that measuring the ankle-brachial index is reasonable for cardiovascular risk assessment in asymptomatic adults at intermediate risk (class IIA—conflicting evidence or divergence of opinion, from multiple randomized clinical trials).⁵¹ Also recommended as risk stratification tools for this patient population are measurement of carotid intima-media thickness and measurement of coronary artery calcium (both class IIA recommendations).

Unlike these tests, however, the ankle-brachial index does not require highly trained technical and medical personnel to perform and interpret. In addition, there is no risk of radiation exposure as is the case in coronary calcium measurement. It is a simpler, lower-cost, and more widely available tool for cardiovascular risk assessment.

LIMITATIONS TO ANKLE-BRACHIAL SCREENING IN PRACTICE

Although this test is relatively simple and noninvasive, it is not widely performed in primary care and cardiovascular medicine. In a study by Mohler and colleagues,⁵² the most common barriers to its use among primary care providers were the time required to perform it, lack of reimbursement for it, and limited staff availability. Currently, third-party payers do not generally reimburse for an ankle-brachial index examination performed to screen a patient who is asymptomatic but at risk for peripheral artery disease. Unfortunately, this has limited the widespread adoption of a program to detect peripheral artery disease in patients at risk.

Despite these limitations, the ankle-brachial index is an invaluable tool to both screen for peripheral artery disease in the appropriate at-risk patient populations and to diagnose it in patients who present with lower extremity symptoms. There are few diagnostic tests available today that provide such a high degree of diagnostic accuracy with as much prognostic information as the ankle-brachial index and with such little expense and risk to the patient.

Over the past 30 years, the focus of treating heart failure has shifted from managing symptoms to prolonging lives. When the neurohormonal hypothesis (ie, the concept that neurohormonal dysregulation and not merely hemodynamic changes are responsible for the onset and progression of heart failure) was introduced, it brought a dramatic change that included new classes of drugs that interfere with the renin-angiotensin-aldosterone system, ie, angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor blockers (ARBs), and, most recently, aldosterone receptor antagonists (ARAs) (Figure 1).

Evidence supporting the use of the ARAs spironolactone (Aldactone) and eplerenone (Inspra) in heart failure has been growing, as has evidence of their usefulness in treating diabetes and chronic renal disease. Still, these drugs must be used cautiously, as they can cause hyperkalemia.

This paper will review the clinical use of ARAs in symptomatic systolic heart failure, their side effects, the findings and implications of recent trials, and controversies in this area, notably whether there is any evidence favoring the use of one drug over another.

ALDOSTERONE IN HEART FAILURE

Aldosterone, a hormone secreted by the zona glomerulosa of the adrenal gland, was first isolated by Simpson and Tait more than half a century ago.¹ Later, it was found to promote reabsorption of sodium and excretion of potassium in the kidneys and hence was categorized as a mineralocorticoid hormone.

Release of aldosterone is stimulated by decreased renal perfusion via angiotensin II, hyperkalemia, and possibly adrenocorticotropic hormone.² Aldosterone exerts its effects by binding to mineralocorticoid receptors in renal epithelial cells.

Aldosterone has several deleterious effects on the failing heart, primarily sodium and fluid retention, but also endothelial dysfunction, left ventricular hypertrophy, and myocardial fibrosis.^2,3 Plasma aldosterone levels can be markedly elevated in patients with heart failure, likely due to activation of the renin-angiotensin-aldosterone system. Elevated aldosterone and angiotensin II levels have been associated with higher mortality rates.⁴

ALDOSTERONE ‘ESCAPE’ BLUNTS THE EFFECT OF ACE INHIBITORS AND ARBs

ACE inhibitors and ARBs have become standards of care for patients with systolic heart failure, and for many years, it was believed that these drugs suppressed aldosterone levels sufficiently. But elevated aldosterone levels have been noted in up to 38% of patients on chronic ACE inhibitor therapy.⁵ In one study, patients on dual blockade, ie, on both an ACE inhibitor and an ARB, had significantly lower aldosterone levels at 17 weeks of therapy, but not at 43 weeks.⁶ This phenomenon is known as “aldosterone escape.”

Several mechanisms might explain this phenomenon. Angiotensin II, a potent inducer of aldosterone, is “reactivated” during long-term ACE inhibitor therapy. Interestingly, patients progress toward aldosterone escape regardless of whether the ACE inhibitor dose is low or high.⁷ There is evidence that some aldosterone is produced by endothelial cells and vascular smooth muscle in the heart and blood vessels,⁸ but ACE inhibitors and ARBs suppress only the aldosterone secreted by the adrenal glands.

Regardless of the mechanism, aldosterone escape can blunt the effects of ACE inhibitors and ARBs, reducing their favorable effects on the risk of death in heart failure patients. This is the rationale for also using ARAs.

ARAs IN HEART FAILURE

Aldosterone acts by regulating gene expression after binding to mineralocorticoid receptors. These receptors are found not only in epithelial tissue in the kidneys and glands, but also in nonepithelial tissues such as cardiomyocytes, vessel walls, and the hippocampus of the brain.⁹ The nonepithelial effects were first demonstrated 2 decades ago by Brilla et al,¹⁰ who noted that chronically elevated aldosterone levels in rats promoted cardiac fibroblast growth, collagen accumulation, and, hence, ventricular remodeling.

The hypertensive effect of aldosterone may also be mediated through mineralocorticoid receptors in the brain. Gomez-Sanchez et al¹¹ found that infusing aldosterone into the cerebral ventricles caused significant hypertension. A selective mineralocorticoid antagonist inhibited this effect when infused into the cerebral ventricles but not when given systemically.

In 1959, Cella and Kagawa created spironolactone, a nonselective ARA, by combining elements of progesterone for its antimineralocorticoid effect and elements of digitoxin for its cardiotonic effect.¹² Although spironolactone is very effective in treating hypertension and heart failure, its use is limited by progestational and antiandrogenic side effects. This led, in 1987, to the invention by de Gasparo et al of a newer molecule, a selective ARA now called eplerenone.¹³ Although eplerenone may be somewhat less potent than spironolactone in blocking mineralocorticoid receptors, no significant difference in efficacy has been noted in randomized clinical trials, and its antiandrogenic action is negligible.¹²

Although these drugs target aldosterone receptors, newer drugs may target different aspects of mineralocorticoid activities, and thus the term “mineralocorticoid receptor antagonist” has been proposed.

TRIALS OF ARAs IN HEART FAILURE

An online data supplement that accompanies this paper at provides a detailed comparison of the three major trials of ARAs in patients with heart failure.

The Randomized Aldactone Evaluation Study (RALES)

The first major clinical trial of an ARA was the Randomized Aldactone Evaluation Study (RALES),¹⁴ a randomized, double-blind, controlled comparison of spironolactone and placebo.

The 1,663 patients in the trial all had severe heart failure (New York Heart Association class [NYHA] III and ambulatory class IV symptoms) and a left ventricular ejection fraction of 35% or less. Most were on an ACE inhibitor, a loop diuretic, and digoxin, but only 10% of patients in both groups were on a beta-blocker. Patients with chronic renal failure (serum creatinine > 2.5 mg/dL) or hyperkalemia (potassium > 5.0 mmol/L) were excluded.

RALES was halted early when an interim analysis at a mean follow-up of 24 months showed that significantly fewer patients were dying in the spironolactone group; their all-cause mortality rate was 30% lower (relative risk [RR] 0.70, 95% confidence interval [CI] 0.60–0.82, P < .001), and their cardiac mortality rate was 31% lower (RR 0.69, 95% CI 0.58–0.82, P < .001). This was concordant with a lower risk of both sudden cardiac death and death from progressive heart failure. The risk of hospitalization for cardiac causes was also 30% lower for patients in the spironolactone group, who also experienced significant symptom improvement.

Gynecomastia and breast pain occurred in about 10% of patients in the spironolactone group, and adverse effects leading to study drug discontinuation occurred in 2%.¹⁴

The Eplerenone Post-acute Myocardial Infarction Heart Failure Efficacy and Survival Study (EPHESUS)

The next landmark trial of an ARA was the Eplerenone Post-acute Myocardial Infarction Heart Failure Efficacy and Survival Study (EPHESUS).¹⁵ A total of 6,632 patients were randomized to receive eplerenone or placebo in this multicenter, double-blind trial. To be enrolled, patients had to have acute myocardial infarction, a left ventricular ejection fraction of 40% or less, and either clinical signs of heart failure 3 to 14 days after the infarction or a history of diabetes mellitus. Patients were excluded if they had chronic kidney disease (defined as a serum creatinine > 2.5 mg/dL or an estimated glomerular filtration rate < 30 mL/min/1.73 m²) or hyperkalemia (a serum potassium > 5.0 mmol/L). All the patients received optimal medical therapy and reperfusion therapy, if warranted.

This event-driven trial was stopped when 1,012 deaths had occurred. During a mean follow-up of 16 months, there was a 15% lower rate of all-cause mortality in the eplerenone group (RR 0.85, 95% CI 0.75–0.96, P = .008) and a 13% lower rate of cardiovascular mortality (RR 0.83, 95% CI 0.72–0.94, P = .005). The reduction in the cardiovascular mortality rate was attributed to a 21% reduction in the rate of sudden cardiac deaths. The rate of heart failure hospitalization was also lower in the eplerenone group.