Cleveland Clinic Journal of Medicine

A 62-year-old man was admitted to the intensive care unit with esophageal variceal bleeding. He had a long history of alcohol abuse with secondary cirrhosis, with a Child-Pugh score of 11 on a scale of 15 (class C—the most severe) at presentation. He also had a history of uncomplicated umbilical hernia, 6 cm in diameter without overlying trophic skin alterations.

Treatment with somatostatin, endoscopic band ligation, and prophylactic antibiotics was initiated for the variceal bleeding. The next day, he was transferred to the hepatology floor. His condition stabilized during the next week, but then he abruptly became diaphoretic and less talkative. Physical examination revealed a painful and irreducible umbilical hernia (Figure 1). He was rushed for umbilical hernia repair with resection of a necrotic segment of small bowel. His recovery after surgery was uneventful, and he was eventually discharged.

UMBILICAL HERNIA AND CIRRHOSIS

Umbilical hernia is common in cirrhotic patients suffering from ascites, with a prevalence up to 20%, which is 10 times higher than in the general population.¹ Ascites is the major predisposing factor since it causes muscle wasting and increases intra-abdominal pressure.

A unique feature of cirrhosis is low physiologic reserve, which increases the risk of death from complications of umbilical hernia and makes the patient more vulnerable to perioperative complications during repair. Because of the high operative risk, umbilical hernia repair has traditionally been reserved for the most complicated cases, such as strangulation of the bowel or rupture of the skin with leakage of ascitic fluid.^2,3 Many patients are thus managed conservatively, with watchful waiting.

However, the natural course of umbilical hernia tends toward complications (eg, bowel incarceration, rupture of the overlying skin), which necessitate urgent repair.⁴ The risk of death with hernia repair in this urgent setting is seven times higher than for elective hernia repair in cirrhotic patients.⁵ More recent data indicate that elective repair in patients with well-compensated cirrhosis carries complication and mortality rates similar to those in noncirrhotic patients.^5–8 Therefore, patients who should undergo umbilical hernia repair are not only those with complicated umbilical hernia (strangulation or ascites leak), but also those with well-compensated cirrhosis at risk of complications.

Factors that pose a particularly high risk of complications of repair are large hernia (> 5 cm), hernia associated with pain, intermittent incarceration, and trophic alterations of the overlying skin.¹ In these patients, elective repair should be considered if hepatic function is preserved, if ascites is well managed (sodium restriction, diuretics, and sometimes even preoperative transjugular intrahepatic portosystemic shunt placement), and if the patient is not expected to undergo liver transplantation in the near future. If liver transplantation is anticipated in the short term, umbilical hernia can be managed concomitantly. Management of ascites after umbilical hernia repair is essential for prevention of recurrence.

A 62-year-old man was admitted to the intensive care unit with esophageal variceal bleeding. He had a long history of alcohol abuse with secondary cirrhosis, with a Child-Pugh score of 11 on a scale of 15 (class C—the most severe) at presentation. He also had a history of uncomplicated umbilical hernia, 6 cm in diameter without overlying trophic skin alterations.

Treatment with somatostatin, endoscopic band ligation, and prophylactic antibiotics was initiated for the variceal bleeding. The next day, he was transferred to the hepatology floor. His condition stabilized during the next week, but then he abruptly became diaphoretic and less talkative. Physical examination revealed a painful and irreducible umbilical hernia (Figure 1). He was rushed for umbilical hernia repair with resection of a necrotic segment of small bowel. His recovery after surgery was uneventful, and he was eventually discharged.

UMBILICAL HERNIA AND CIRRHOSIS

Umbilical hernia is common in cirrhotic patients suffering from ascites, with a prevalence up to 20%, which is 10 times higher than in the general population.¹ Ascites is the major predisposing factor since it causes muscle wasting and increases intra-abdominal pressure.

A unique feature of cirrhosis is low physiologic reserve, which increases the risk of death from complications of umbilical hernia and makes the patient more vulnerable to perioperative complications during repair. Because of the high operative risk, umbilical hernia repair has traditionally been reserved for the most complicated cases, such as strangulation of the bowel or rupture of the skin with leakage of ascitic fluid.^2,3 Many patients are thus managed conservatively, with watchful waiting.

However, the natural course of umbilical hernia tends toward complications (eg, bowel incarceration, rupture of the overlying skin), which necessitate urgent repair.⁴ The risk of death with hernia repair in this urgent setting is seven times higher than for elective hernia repair in cirrhotic patients.⁵ More recent data indicate that elective repair in patients with well-compensated cirrhosis carries complication and mortality rates similar to those in noncirrhotic patients.^5–8 Therefore, patients who should undergo umbilical hernia repair are not only those with complicated umbilical hernia (strangulation or ascites leak), but also those with well-compensated cirrhosis at risk of complications.

Factors that pose a particularly high risk of complications of repair are large hernia (> 5 cm), hernia associated with pain, intermittent incarceration, and trophic alterations of the overlying skin.¹ In these patients, elective repair should be considered if hepatic function is preserved, if ascites is well managed (sodium restriction, diuretics, and sometimes even preoperative transjugular intrahepatic portosystemic shunt placement), and if the patient is not expected to undergo liver transplantation in the near future. If liver transplantation is anticipated in the short term, umbilical hernia can be managed concomitantly. Management of ascites after umbilical hernia repair is essential for prevention of recurrence.

A 62-year-old man was admitted to the intensive care unit with esophageal variceal bleeding. He had a long history of alcohol abuse with secondary cirrhosis, with a Child-Pugh score of 11 on a scale of 15 (class C—the most severe) at presentation. He also had a history of uncomplicated umbilical hernia, 6 cm in diameter without overlying trophic skin alterations.

Treatment with somatostatin, endoscopic band ligation, and prophylactic antibiotics was initiated for the variceal bleeding. The next day, he was transferred to the hepatology floor. His condition stabilized during the next week, but then he abruptly became diaphoretic and less talkative. Physical examination revealed a painful and irreducible umbilical hernia (Figure 1). He was rushed for umbilical hernia repair with resection of a necrotic segment of small bowel. His recovery after surgery was uneventful, and he was eventually discharged.

UMBILICAL HERNIA AND CIRRHOSIS

Umbilical hernia is common in cirrhotic patients suffering from ascites, with a prevalence up to 20%, which is 10 times higher than in the general population.¹ Ascites is the major predisposing factor since it causes muscle wasting and increases intra-abdominal pressure.

A unique feature of cirrhosis is low physiologic reserve, which increases the risk of death from complications of umbilical hernia and makes the patient more vulnerable to perioperative complications during repair. Because of the high operative risk, umbilical hernia repair has traditionally been reserved for the most complicated cases, such as strangulation of the bowel or rupture of the skin with leakage of ascitic fluid.^2,3 Many patients are thus managed conservatively, with watchful waiting.

However, the natural course of umbilical hernia tends toward complications (eg, bowel incarceration, rupture of the overlying skin), which necessitate urgent repair.⁴ The risk of death with hernia repair in this urgent setting is seven times higher than for elective hernia repair in cirrhotic patients.⁵ More recent data indicate that elective repair in patients with well-compensated cirrhosis carries complication and mortality rates similar to those in noncirrhotic patients.^5–8 Therefore, patients who should undergo umbilical hernia repair are not only those with complicated umbilical hernia (strangulation or ascites leak), but also those with well-compensated cirrhosis at risk of complications.

Factors that pose a particularly high risk of complications of repair are large hernia (> 5 cm), hernia associated with pain, intermittent incarceration, and trophic alterations of the overlying skin.¹ In these patients, elective repair should be considered if hepatic function is preserved, if ascites is well managed (sodium restriction, diuretics, and sometimes even preoperative transjugular intrahepatic portosystemic shunt placement), and if the patient is not expected to undergo liver transplantation in the near future. If liver transplantation is anticipated in the short term, umbilical hernia can be managed concomitantly. Management of ascites after umbilical hernia repair is essential for prevention of recurrence.

A 49-year-old woman with a history of depression, bipolar disorder, and chronic back pain was brought to the emergency department unresponsive after having taken an unknown quantity of amitriptyline tablets.

On arrival, she was comatose, with a score of 3 (the lowest possible score) on the 15-point Glasgow Coma Scale. Her blood pressure was 65/22 mm Hg, heart rate 121 beats per minute, respiratory rate 14 per minute, and oxygen saturation 88% on room air. The rest of the initial physical examination was normal.

She was immediately intubated, put on mechanical ventilation, and given an infusion of a 1-L bolus of normal saline and 50 mmol (1 mmol/kg) of sodium bicarbonate. Norepinephrine infusion was started. Gastric lavage was not done.

Results of initial laboratory testing showed a serum potassium of 2.9 mmol/L (reference range 3.5–5.0) and a serum magnesium of 1.6 mmol/L (1.7–2.6), which were corrected with infusion of 60 mmol of potassium chloride and 2 g of magnesium sulfate. The serum amitriptyline measurement was ordered at the time of her presentation to the emergency department.

Arterial blood gas analysis showed:

• pH 7.15 (normal range 7.35–7.45)
• Paco₂ 66 mm Hg (34–46)
• Pao₂ 229 mm Hg (85–95)
• Bicarbonate 22 mmol/L (22–26).

The initial electrocardiogram (ECG) (Figure 1) showed regular wide-complex tachycardia with no definite right or left bundle branch block morphology, no discernible P waves, a QRS duration of 198 msec, right axis deviation, and no Brugada criteria to suggest ventricular tachycardia.

She remained hypotensive, with regular wide-complex tachycardia on the ECG. She was given an additional 1-L bolus of normal saline and 100 mmol (2 mmol/kg) of sodium bicarbonate, and within 1 minute the wide-complex tachycardia resolved to narrow-complex sinus tachycardia (Figure 2). At this point, an infusion of 150 mmol/L of sodium bicarbonate in dextrose 5% in water was started, with serial ECGs to monitor the QRS duration and serial arterial blood gas monitoring to maintain the pH between 7.45 and 7.55.

TRANSFER TO THE ICU

She was then transferred to the intensive care unit (ICU), where she remained for 2 weeks. While in the ICU, she had a single recurrence of wide-complex tachycardia that resolved immediately with an infusion of 100 mmol of sodium bicarbonate. A urine toxicology screen was negative, and the serum amitriptyline measurement, returned from the laboratory 48 hours after her initial presentation, was 594 ng/mL (reference range 100–250 ng/mL). She was eventually weaned off the norepinephrine infusion after 20 hours, the sodium bicarbonate infusion was discontinued after 4 days, and she was taken off mechanical ventilation after 10 days. Also during her ICU stay, she had seizures on day 3 and developed aspiration pneumonia.

From the ICU, she was transferred to a regular floor, where she stayed for another week and then was transferred to a rehabilitation center. This patient was known to have clinical depression and to have attempted suicide once before. She had recently been under additional psychosocial stresses, which likely prompted this second attempt.

She reportedly had no neurologic or cardiovascular sequelae after her discharge from the hospital.

AMITRIPTYLINE OVERDOSE

Amitriptyline causes a relatively high number of fatal overdoses, at 34 per 1 million prescriptions.¹ Death is usually from hypotension and ventricular arrhythmia caused by blockage of cardiac fast sodium channels leading to disturbances of cardiac conduction such as wide-complex tachycardia.

Other manifestations of amitriptyline overdose include seizures, sedation, and anticholinergic toxicity from variable blockade of gamma-aminobutyric acid receptors, histamine 1 receptors, and alpha receptors.²

In amitriptyline overdose, sinus tachycardia is the most common finding on ECG

Of the various changes on ECG described with amitriptyline overdose, sinus tachycardia is the most common. A QRS duration greater than 100 msec, right to extreme-right axis deviation with negative QRS complexes in leads I and aVL, and an R-wave amplitude greater than 3 mm in lead aVR are indications for sodium bicarbonate infusion, especially in hemodynamically unstable patients.³ Sodium bicarbonate increases the serum concentration of sodium and thereby overcomes the sodium channel blockade. It also alkalinizes the serum, favoring an electrically neutral form of amitriptyline that binds less to receptors and binds more to alpha-1-acid glycoprotein, decreasing the fraction of free drug available for toxicity.⁴

In patients with amitriptyline overdose, wide-complex tachycardia and hypotension refractory to sodium bicarbonate infusion can be treated with lidocaine, magnesium sulfate, direct-current cardioversion, and lipid resuscitation.^5,6 Treatment with class IA, IC, and III antiarrhythmics is contraindicated, as they block sodium channels and thus can worsen conduction disturbances.

A 49-year-old woman with a history of depression, bipolar disorder, and chronic back pain was brought to the emergency department unresponsive after having taken an unknown quantity of amitriptyline tablets.

On arrival, she was comatose, with a score of 3 (the lowest possible score) on the 15-point Glasgow Coma Scale. Her blood pressure was 65/22 mm Hg, heart rate 121 beats per minute, respiratory rate 14 per minute, and oxygen saturation 88% on room air. The rest of the initial physical examination was normal.

She was immediately intubated, put on mechanical ventilation, and given an infusion of a 1-L bolus of normal saline and 50 mmol (1 mmol/kg) of sodium bicarbonate. Norepinephrine infusion was started. Gastric lavage was not done.

Results of initial laboratory testing showed a serum potassium of 2.9 mmol/L (reference range 3.5–5.0) and a serum magnesium of 1.6 mmol/L (1.7–2.6), which were corrected with infusion of 60 mmol of potassium chloride and 2 g of magnesium sulfate. The serum amitriptyline measurement was ordered at the time of her presentation to the emergency department.

Arterial blood gas analysis showed:

• pH 7.15 (normal range 7.35–7.45)
• Paco₂ 66 mm Hg (34–46)
• Pao₂ 229 mm Hg (85–95)
• Bicarbonate 22 mmol/L (22–26).

The initial electrocardiogram (ECG) (Figure 1) showed regular wide-complex tachycardia with no definite right or left bundle branch block morphology, no discernible P waves, a QRS duration of 198 msec, right axis deviation, and no Brugada criteria to suggest ventricular tachycardia.

She remained hypotensive, with regular wide-complex tachycardia on the ECG. She was given an additional 1-L bolus of normal saline and 100 mmol (2 mmol/kg) of sodium bicarbonate, and within 1 minute the wide-complex tachycardia resolved to narrow-complex sinus tachycardia (Figure 2). At this point, an infusion of 150 mmol/L of sodium bicarbonate in dextrose 5% in water was started, with serial ECGs to monitor the QRS duration and serial arterial blood gas monitoring to maintain the pH between 7.45 and 7.55.

TRANSFER TO THE ICU

She was then transferred to the intensive care unit (ICU), where she remained for 2 weeks. While in the ICU, she had a single recurrence of wide-complex tachycardia that resolved immediately with an infusion of 100 mmol of sodium bicarbonate. A urine toxicology screen was negative, and the serum amitriptyline measurement, returned from the laboratory 48 hours after her initial presentation, was 594 ng/mL (reference range 100–250 ng/mL). She was eventually weaned off the norepinephrine infusion after 20 hours, the sodium bicarbonate infusion was discontinued after 4 days, and she was taken off mechanical ventilation after 10 days. Also during her ICU stay, she had seizures on day 3 and developed aspiration pneumonia.

From the ICU, she was transferred to a regular floor, where she stayed for another week and then was transferred to a rehabilitation center. This patient was known to have clinical depression and to have attempted suicide once before. She had recently been under additional psychosocial stresses, which likely prompted this second attempt.

She reportedly had no neurologic or cardiovascular sequelae after her discharge from the hospital.

AMITRIPTYLINE OVERDOSE

Amitriptyline causes a relatively high number of fatal overdoses, at 34 per 1 million prescriptions.¹ Death is usually from hypotension and ventricular arrhythmia caused by blockage of cardiac fast sodium channels leading to disturbances of cardiac conduction such as wide-complex tachycardia.

Other manifestations of amitriptyline overdose include seizures, sedation, and anticholinergic toxicity from variable blockade of gamma-aminobutyric acid receptors, histamine 1 receptors, and alpha receptors.²

In amitriptyline overdose, sinus tachycardia is the most common finding on ECG

Of the various changes on ECG described with amitriptyline overdose, sinus tachycardia is the most common. A QRS duration greater than 100 msec, right to extreme-right axis deviation with negative QRS complexes in leads I and aVL, and an R-wave amplitude greater than 3 mm in lead aVR are indications for sodium bicarbonate infusion, especially in hemodynamically unstable patients.³ Sodium bicarbonate increases the serum concentration of sodium and thereby overcomes the sodium channel blockade. It also alkalinizes the serum, favoring an electrically neutral form of amitriptyline that binds less to receptors and binds more to alpha-1-acid glycoprotein, decreasing the fraction of free drug available for toxicity.⁴

In patients with amitriptyline overdose, wide-complex tachycardia and hypotension refractory to sodium bicarbonate infusion can be treated with lidocaine, magnesium sulfate, direct-current cardioversion, and lipid resuscitation.^5,6 Treatment with class IA, IC, and III antiarrhythmics is contraindicated, as they block sodium channels and thus can worsen conduction disturbances.

A 49-year-old woman with a history of depression, bipolar disorder, and chronic back pain was brought to the emergency department unresponsive after having taken an unknown quantity of amitriptyline tablets.

On arrival, she was comatose, with a score of 3 (the lowest possible score) on the 15-point Glasgow Coma Scale. Her blood pressure was 65/22 mm Hg, heart rate 121 beats per minute, respiratory rate 14 per minute, and oxygen saturation 88% on room air. The rest of the initial physical examination was normal.

She was immediately intubated, put on mechanical ventilation, and given an infusion of a 1-L bolus of normal saline and 50 mmol (1 mmol/kg) of sodium bicarbonate. Norepinephrine infusion was started. Gastric lavage was not done.

Results of initial laboratory testing showed a serum potassium of 2.9 mmol/L (reference range 3.5–5.0) and a serum magnesium of 1.6 mmol/L (1.7–2.6), which were corrected with infusion of 60 mmol of potassium chloride and 2 g of magnesium sulfate. The serum amitriptyline measurement was ordered at the time of her presentation to the emergency department.

Arterial blood gas analysis showed:

• pH 7.15 (normal range 7.35–7.45)
• Paco₂ 66 mm Hg (34–46)
• Pao₂ 229 mm Hg (85–95)
• Bicarbonate 22 mmol/L (22–26).

The initial electrocardiogram (ECG) (Figure 1) showed regular wide-complex tachycardia with no definite right or left bundle branch block morphology, no discernible P waves, a QRS duration of 198 msec, right axis deviation, and no Brugada criteria to suggest ventricular tachycardia.

She remained hypotensive, with regular wide-complex tachycardia on the ECG. She was given an additional 1-L bolus of normal saline and 100 mmol (2 mmol/kg) of sodium bicarbonate, and within 1 minute the wide-complex tachycardia resolved to narrow-complex sinus tachycardia (Figure 2). At this point, an infusion of 150 mmol/L of sodium bicarbonate in dextrose 5% in water was started, with serial ECGs to monitor the QRS duration and serial arterial blood gas monitoring to maintain the pH between 7.45 and 7.55.

TRANSFER TO THE ICU

She was then transferred to the intensive care unit (ICU), where she remained for 2 weeks. While in the ICU, she had a single recurrence of wide-complex tachycardia that resolved immediately with an infusion of 100 mmol of sodium bicarbonate. A urine toxicology screen was negative, and the serum amitriptyline measurement, returned from the laboratory 48 hours after her initial presentation, was 594 ng/mL (reference range 100–250 ng/mL). She was eventually weaned off the norepinephrine infusion after 20 hours, the sodium bicarbonate infusion was discontinued after 4 days, and she was taken off mechanical ventilation after 10 days. Also during her ICU stay, she had seizures on day 3 and developed aspiration pneumonia.

From the ICU, she was transferred to a regular floor, where she stayed for another week and then was transferred to a rehabilitation center. This patient was known to have clinical depression and to have attempted suicide once before. She had recently been under additional psychosocial stresses, which likely prompted this second attempt.

She reportedly had no neurologic or cardiovascular sequelae after her discharge from the hospital.

AMITRIPTYLINE OVERDOSE

Amitriptyline causes a relatively high number of fatal overdoses, at 34 per 1 million prescriptions.¹ Death is usually from hypotension and ventricular arrhythmia caused by blockage of cardiac fast sodium channels leading to disturbances of cardiac conduction such as wide-complex tachycardia.

Other manifestations of amitriptyline overdose include seizures, sedation, and anticholinergic toxicity from variable blockade of gamma-aminobutyric acid receptors, histamine 1 receptors, and alpha receptors.²

In amitriptyline overdose, sinus tachycardia is the most common finding on ECG

Of the various changes on ECG described with amitriptyline overdose, sinus tachycardia is the most common. A QRS duration greater than 100 msec, right to extreme-right axis deviation with negative QRS complexes in leads I and aVL, and an R-wave amplitude greater than 3 mm in lead aVR are indications for sodium bicarbonate infusion, especially in hemodynamically unstable patients.³ Sodium bicarbonate increases the serum concentration of sodium and thereby overcomes the sodium channel blockade. It also alkalinizes the serum, favoring an electrically neutral form of amitriptyline that binds less to receptors and binds more to alpha-1-acid glycoprotein, decreasing the fraction of free drug available for toxicity.⁴

In patients with amitriptyline overdose, wide-complex tachycardia and hypotension refractory to sodium bicarbonate infusion can be treated with lidocaine, magnesium sulfate, direct-current cardioversion, and lipid resuscitation.^5,6 Treatment with class IA, IC, and III antiarrhythmics is contraindicated, as they block sodium channels and thus can worsen conduction disturbances.

The art of medicine includes picking the right drug for the right patient, especially when we can choose between different classes of efficacious therapies. But, in view of our growing understanding of the human genome, can science replace art?

That question is part of the promise of pharmacogenetics, the study of how inter-individual genetic differences influence a patient’s response to a specific drug. A patient’s genome dictates the expression of specific enzymes that metabolize a drug with various efficiencies: variant alleles may result in slightly different proteins that express different enzymatic activity, ie, different substrate affinities for a drug resulting in more or less efficient metabolism. Genomic differences may also dictate whether a specific biochemical pathway is dominant in generating a specific pathophysiologic response, in which case drugs that affect that pathway may be strikingly effective. This may partly explain the various responses to different antihypertensive drugs.

Another less well-understood example of pharmacogenetics is the link between specific HLA haplotypes and a dramatic increase in allergic reactions to specific medications, such as the link between HLA-B*57:01 and abacavir hypersensitivity.

In this issue of the Journal, DiPiero et al discuss thiopurine methyltransferase (TPMT), an enzyme responsible for the degradation of azathioprine, and how knowing the genetically determined relative activity of this enzyme should influence our initial dosing of this and related drugs. Patients with certain variant alleles of TPMT degrade azathioprine more slowly, and these patients are at higher risk of myelosuppressive toxicity from the drug when it is given at the full weight-based dose. The TPMT test is expensive but not prohibitively so, and it would seem that genomic testing is a reasonable clinical and cost-effective option.

As in the abacavir scenario noted above, genomic-based dosing of azathioprine makes scientific sense and offers proof of principle for the validity of pharmacogenomics. But is it truly a clinical game-changer?

The answer depends in part on how the prescribing physician doses the drug, which depends in part on what disease is being treated, how fast the drug needs to be at full dose, and whether there are equally effective alternatives. Recommendations have been offered that state if TPMT activity is normal, we can start at the usual maintenance dose of 1.5 to 2 mg/kg/day (or occasionally more). But if the patient is heterozygous for the wild-type gene and thus is a slower drug metabolizer, then initial dosing “should” be reduced to 25 to 50 mg/day, with close observation of the white blood cell count as the dose is slowly increased to the target. The very rare patient who is homozygous for a non–wild-type allele should not be given the drug.

My usual practice has been to start patients on 50 mg or less daily and slowly titrate up, asking them how they are tolerating the drug and watching the white count—notably, the same approach to be taken if I had done genotyping before starting the drug and had found the patient to be heterozygous for the TPMT gene.

Interestingly, one pragmatic clinical trial tested whether genotyping patients before starting azathioprine—with subsequent suggested dosing of the drug based on the genotype as above—was safer and cheaper than letting physicians dose as they chose.¹ It turned out that physicians participating in this study still dosed their patients conservatively. Even knowing that they might be able to give full doses from the start in patients with normal TPMT activity, many chose not to. I assume that many of those physicians felt as I do that there was no urgency in reaching the presumed-to-be-effective full weight-based therapeutic dose. (We don’t have a good clinical marker of azathioprine’s efficacy). At 4 months, the maintenance dose was about the same in all groups.

We have robust evidence to support the role of pharmacogenetics in informing the dosing of several medications, more than just the ones I have mentioned here. And in the right settings, we should use pharmacogenetic testing to limit toxicity and perhaps enhance efficacy in our drug selection. As the field moves rapidly forward, we will have many opportunities to improve clinical care by using our patients’ genomic information.

But like it or bemoan it, even when we have science in the house, the art of medicine still plays a role in our clinical decisions.

The art of medicine includes picking the right drug for the right patient, especially when we can choose between different classes of efficacious therapies. But, in view of our growing understanding of the human genome, can science replace art?

That question is part of the promise of pharmacogenetics, the study of how inter-individual genetic differences influence a patient’s response to a specific drug. A patient’s genome dictates the expression of specific enzymes that metabolize a drug with various efficiencies: variant alleles may result in slightly different proteins that express different enzymatic activity, ie, different substrate affinities for a drug resulting in more or less efficient metabolism. Genomic differences may also dictate whether a specific biochemical pathway is dominant in generating a specific pathophysiologic response, in which case drugs that affect that pathway may be strikingly effective. This may partly explain the various responses to different antihypertensive drugs.

Another less well-understood example of pharmacogenetics is the link between specific HLA haplotypes and a dramatic increase in allergic reactions to specific medications, such as the link between HLA-B*57:01 and abacavir hypersensitivity.

In this issue of the Journal, DiPiero et al discuss thiopurine methyltransferase (TPMT), an enzyme responsible for the degradation of azathioprine, and how knowing the genetically determined relative activity of this enzyme should influence our initial dosing of this and related drugs. Patients with certain variant alleles of TPMT degrade azathioprine more slowly, and these patients are at higher risk of myelosuppressive toxicity from the drug when it is given at the full weight-based dose. The TPMT test is expensive but not prohibitively so, and it would seem that genomic testing is a reasonable clinical and cost-effective option.

As in the abacavir scenario noted above, genomic-based dosing of azathioprine makes scientific sense and offers proof of principle for the validity of pharmacogenomics. But is it truly a clinical game-changer?

The answer depends in part on how the prescribing physician doses the drug, which depends in part on what disease is being treated, how fast the drug needs to be at full dose, and whether there are equally effective alternatives. Recommendations have been offered that state if TPMT activity is normal, we can start at the usual maintenance dose of 1.5 to 2 mg/kg/day (or occasionally more). But if the patient is heterozygous for the wild-type gene and thus is a slower drug metabolizer, then initial dosing “should” be reduced to 25 to 50 mg/day, with close observation of the white blood cell count as the dose is slowly increased to the target. The very rare patient who is homozygous for a non–wild-type allele should not be given the drug.

My usual practice has been to start patients on 50 mg or less daily and slowly titrate up, asking them how they are tolerating the drug and watching the white count—notably, the same approach to be taken if I had done genotyping before starting the drug and had found the patient to be heterozygous for the TPMT gene.

Interestingly, one pragmatic clinical trial tested whether genotyping patients before starting azathioprine—with subsequent suggested dosing of the drug based on the genotype as above—was safer and cheaper than letting physicians dose as they chose.¹ It turned out that physicians participating in this study still dosed their patients conservatively. Even knowing that they might be able to give full doses from the start in patients with normal TPMT activity, many chose not to. I assume that many of those physicians felt as I do that there was no urgency in reaching the presumed-to-be-effective full weight-based therapeutic dose. (We don’t have a good clinical marker of azathioprine’s efficacy). At 4 months, the maintenance dose was about the same in all groups.

We have robust evidence to support the role of pharmacogenetics in informing the dosing of several medications, more than just the ones I have mentioned here. And in the right settings, we should use pharmacogenetic testing to limit toxicity and perhaps enhance efficacy in our drug selection. As the field moves rapidly forward, we will have many opportunities to improve clinical care by using our patients’ genomic information.

But like it or bemoan it, even when we have science in the house, the art of medicine still plays a role in our clinical decisions.

The art of medicine includes picking the right drug for the right patient, especially when we can choose between different classes of efficacious therapies. But, in view of our growing understanding of the human genome, can science replace art?

That question is part of the promise of pharmacogenetics, the study of how inter-individual genetic differences influence a patient’s response to a specific drug. A patient’s genome dictates the expression of specific enzymes that metabolize a drug with various efficiencies: variant alleles may result in slightly different proteins that express different enzymatic activity, ie, different substrate affinities for a drug resulting in more or less efficient metabolism. Genomic differences may also dictate whether a specific biochemical pathway is dominant in generating a specific pathophysiologic response, in which case drugs that affect that pathway may be strikingly effective. This may partly explain the various responses to different antihypertensive drugs.

Another less well-understood example of pharmacogenetics is the link between specific HLA haplotypes and a dramatic increase in allergic reactions to specific medications, such as the link between HLA-B*57:01 and abacavir hypersensitivity.

In this issue of the Journal, DiPiero et al discuss thiopurine methyltransferase (TPMT), an enzyme responsible for the degradation of azathioprine, and how knowing the genetically determined relative activity of this enzyme should influence our initial dosing of this and related drugs. Patients with certain variant alleles of TPMT degrade azathioprine more slowly, and these patients are at higher risk of myelosuppressive toxicity from the drug when it is given at the full weight-based dose. The TPMT test is expensive but not prohibitively so, and it would seem that genomic testing is a reasonable clinical and cost-effective option.

As in the abacavir scenario noted above, genomic-based dosing of azathioprine makes scientific sense and offers proof of principle for the validity of pharmacogenomics. But is it truly a clinical game-changer?

The answer depends in part on how the prescribing physician doses the drug, which depends in part on what disease is being treated, how fast the drug needs to be at full dose, and whether there are equally effective alternatives. Recommendations have been offered that state if TPMT activity is normal, we can start at the usual maintenance dose of 1.5 to 2 mg/kg/day (or occasionally more). But if the patient is heterozygous for the wild-type gene and thus is a slower drug metabolizer, then initial dosing “should” be reduced to 25 to 50 mg/day, with close observation of the white blood cell count as the dose is slowly increased to the target. The very rare patient who is homozygous for a non–wild-type allele should not be given the drug.

My usual practice has been to start patients on 50 mg or less daily and slowly titrate up, asking them how they are tolerating the drug and watching the white count—notably, the same approach to be taken if I had done genotyping before starting the drug and had found the patient to be heterozygous for the TPMT gene.

Interestingly, one pragmatic clinical trial tested whether genotyping patients before starting azathioprine—with subsequent suggested dosing of the drug based on the genotype as above—was safer and cheaper than letting physicians dose as they chose.¹ It turned out that physicians participating in this study still dosed their patients conservatively. Even knowing that they might be able to give full doses from the start in patients with normal TPMT activity, many chose not to. I assume that many of those physicians felt as I do that there was no urgency in reaching the presumed-to-be-effective full weight-based therapeutic dose. (We don’t have a good clinical marker of azathioprine’s efficacy). At 4 months, the maintenance dose was about the same in all groups.

We have robust evidence to support the role of pharmacogenetics in informing the dosing of several medications, more than just the ones I have mentioned here. And in the right settings, we should use pharmacogenetic testing to limit toxicity and perhaps enhance efficacy in our drug selection. As the field moves rapidly forward, we will have many opportunities to improve clinical care by using our patients’ genomic information.

But like it or bemoan it, even when we have science in the house, the art of medicine still plays a role in our clinical decisions.

The thiopurines azathioprine, mercaptopurine, and thioguanine are prodrugs that are converted to active thioguanine nucleotide metabolites or methylated by thiopurine methyltransferase (TPMT) to compounds with less pharmacologic activity. In the absence of TPMT activity, patients are likely to have higher concentrations of thioguanine nucleotides, which can pose an increased risk of severe life-threatening myelosuppression. Determining TPMT activity, either directly by phenotyping or indirectly by determining the specific genetic allele (different alleles have different enzymatic activity), can help identify patients at greater risk of severe myelosuppression. Therefore, we recommend that TPMT testing be strongly considered before initiating therapy with a thiopurine.

THIOPURINES AND TPMT

Azathioprine, mercaptopurine, and thioguanine are used for treating autoimmune and inflammatory diseases^1–3 and certain types of cancer such as leukemias and lymphomas.^1,4–6 Typically, azathioprine is used to treat nonmalignant conditions, thioguanine is used to treat malignancies, and mercaptopurine can be used to treat both malignant and nonmalignant conditions.

Although the exact mechanism of action of these drugs has not been completely elucidated, the active thioguanine nucleotide metabolites are thought to be incorporated into the DNA of leukocytes, resulting in DNA damage that subsequently leads to cell death and myelosuppression.^7–9

Variants of the TPMT gene may alter the activity of the TPMT enzyme, resulting in individual variability in thiopurine metabolism. Compared with people with normal (high) TPMT activity, those with intermediate or low TPMT activity metabolize the drugs more slowly, and are likely to have higher thioguanine nucleotide concentrations and therefore an increased risk of myelosuppression.

One of the earliest correlations between TPMT activity and thiopurine-induced myelosuppression was described in a pediatric patient with acute lymphocytic leukemia.¹⁰ After being prescribed a conventional mercaptopurine dosage (75 mg/m² daily), the patient developed severe myelosuppression and was observed to have a thioguanine nucleotide metabolite concentration seven times the observed population median. TPMT phenotyping demonstrated that the patient had low TPMT activity. Reducing the mercaptopurine dose by approximately 90% resulted in normalization of thioguanine nucleotide metabolite concentrations, and the myelosuppression subsequently resolved.

Approximately 10% of the population has intermediate TPMT activity and 0.3% has low or absent TPMT activity, though these percentages vary depending on ancestry.¹ Research has demonstrated that approximately 30% to 60% of those with intermediate TPMT activity cannot tolerate a full thiopurine dose (eg, azathioprine 2–3 mg/kg/day or mercaptopurine 1.5 mg/kg/day).¹ Almost all patients with low TPMT activity will develop life-threating myelosuppression if prescribed a full thiopurine dose.¹

SHOULD TPMT ACTIVITY BE DETERMINED FOR EVERY PATIENT PRESCRIBED A THIOPURINE?

Although determining TPMT activity in thiopurine-naïve patients will assist clinicians in selecting a thiopurine starting dose or in deciding if an alternative agent is warranted, there are instances when a clinician may elect to not perform a TPMT genotype or phenotype test. For example, determining TPMT activity is not recommended for patients who previously tolerated thiopurine therapy at full steady-state doses.

The required starting dose of a thiopurine can influence the decision on whether or not to test for TPMT activity. TPMT genotyping or phenotyping may be of most benefit for patients requiring immediate full doses of a thiopurine.¹¹ Ideally, TPMT activity should be determined before prescribing immediate full doses of a thiopurine. This could be achieved by preemptively ordering a TPMT test in patients likely to require immunosuppression—for example, in patients diagnosed with inflammatory or autoimmune diseases. If therapy cannot be delayed and TPMT activity is unknown, ordering a TPMT test at the time of prescribing a full thiopurine dose is still of benefit. Depending on the clinical laboratory utilized for testing, TPMT phenotype results are usually reported in 3 to 5 days, and TPMT genotype results are usually reported in 5 to 7 days. Because most patients will not reach steady-state concentrations for 2 to 6 weeks, clinicians could initiate immediate full doses of a thiopurine and modify therapy based on TPMT test results before accumulation of thioguanine nucleotide metabolites occurs. Caution should be used with this approach, particularly in situations where the clinical laboratory may not return results in a timely manner.

For patients who are candidates for an initial low dose of a thiopurine, clinicians may choose to slowly titrate doses based on response and tolerability instead of determining TPMT activity.¹¹ Depending on the starting dose and how slowly titration occurs, initiating a thiopurine at a low dose and titrating based on response can be a feasible approach for patients with intermediate TPMT activity. Because drastic thiopurine dose reductions of approximately 10-fold are required for patients with low TPMT activity, which is a much smaller dosage than most clinicians will initially prescribe, the starting dosage will likely not be low enough to prevent myelosuppression in patients with low TPMT activity.^1,10

Determining TPMT activity can help clinicians establish an appropriate titration schedule. Patients with normal TPMT activity will usually reach thiopurine steady-state concentrations in 2 weeks, and the dosage can be titrated based on response.¹ Alterations in TPMT activity influence the pharmacokinetic parameters of thiopurines, and the time to reach steady-state is extended to 4 or 6 weeks for those with intermediate or low TPMT activity.¹ Increasing the thiopurine dosage before reaching steady state can lead to the prescribing of doses that will not be tolerated, resulting in myelosuppression.

Factors to consider when deciding if TPMT activity should be assessed include the disease state being treated and corresponding starting dose, the need for immediate full doses, and previous documented tolerance of thiopurines at steady-state doses. As with many aspects of medicine that have multiple options, coupled with an increase in patient access to healthcare information, the decision to test for TPMT activity may include shared decision-making between patients and providers. Although TPMT genotyping or phenotyping can help identify those at greatest risk of severe myelosuppression, such assays do not replace routine monitoring for myelosuppression, hepatotoxicity, or pancreatitis that may be caused by thiopurines.

WHAT TESTS ARE AVAILABLE TO DETERMINE TPMT ACTIVITY?

Patients with intermediate or low TPMT activity can be identified by either genotyping or phenotyping. There are considerations, though, that clinicians should be aware of before selecting a particular test.

TPMT genotyping

Four TPMT alleles, TPMT*2, *3A, *3B, and *3C, account for over 90% of inactivating polymorphisms.¹² Therefore, most reference laboratories only analyze for those genetic variants. Based on the reported test result, a predicted phenotype (eg, normal, intermediate, or low TPMT activity) can be assigned. Table 1 lists the predicted phenotypes for select genotyping results.

TPMT phenotyping

Phenotyping quantitates TPMT enzyme activity in erythrocytes, and based on the result, patients are classified as having normal, intermediate, or low TPMT activity. Because internal standards and other testing conditions may differ between reference laboratories, test results must be interpreted in the context of the laboratory that performed the assay.

Which test is right for my patient?

In most cases, either the genotype or the phenotype test provides sufficient information to guide thiopurine therapy. There are certain circumstances, though, in which the genotype or phenotype test is less informative.

TPMT genotyping, when performed using a blood specimen, is not recommended in those with a history of allogeneic bone marrow transplantation, as the result would reflect the donor’s genotype, not the patient’s. In such instances, monitoring of white blood cell counts and thiopurine metabolites may be more beneficial.

TPMT phenotyping may be inaccurate if performed within 30 to 90 days of an erythrocyte transfusion, as the test result may be influenced by donor erythrocytes. If a patient is receiving erythrocyte transfusions, TPMT genotyping is preferable to phenotyping.

Test cost may also be a consideration when determining if the genotype or phenotype test is best for your patient. Costs vary by laboratory, but phenotyping is generally less expensive than genotyping. The cost of genotyping, though, continues to decrease.¹³ The approximate commercial cost is $200 for phenotyping and $450 for genotyping, but laboratory fees may be substantially higher. Several insurance plans, including Medicare, cover TPMT testing, but reimbursement and copayments vary, depending on the patient’s specific plan.

There are conflicting data as to whether determining TPMT status is^11,14–18 or is not¹⁹ cost-effective. Multiple studies suggest that the cost of genotyping a sufficient number of patients to identify a single individual at high risk of myelosuppression is cheaper than the costs associated with treating an adverse event. Additional cost-benefit studies are needed, particularly studies that consider how bundled payments and outcomes-based reimbursement influence cost-effectiveness.

MODIFYING THIOPURINE THERAPY BASED ON TPMT ACTIVITY

There is a strong correlation between TPMT activity and tolerated thiopurine doses, with those having intermediate or low TPMT activity requiring lower doses.^10,20–23 Adjusting mercaptopurine doses based on TPMT activity to prevent hematopoietic toxicity has been successfully demonstrated in pediatric patients with acute lymphoblastic leukemia.²⁴ Furthermore, reducing initial thiopurine doses to avoid myelosuppression and titrating based on response has been shown to not compromise outcomes.^1,25,26 The Clinical Pharmacogenetic Implementation Consortium (CPIC) has developed an evidence-based guideline on how to adjust thiopurine doses based on TPMT activity,¹ summarized in Table 2. These dosing recommendations are classified as “strong.”

Patients with normal TPMT activity should be prescribed the usual thiopurine starting dose as indicated by disease-specific guidelines.

For those with intermediate TPMT activity, the CPIC guideline recommends reducing the initial targeted full dose of azathioprine and mercaptopurine by 30% to 70% and reducing the targeted full dose of thioguanine by 30% to 50%. The percentage of dose reduction depends on the targeted full dose. Siegel and Sands²⁷ suggested that for those who are diagnosed with inflammatory bowel disease and have intermediate TPMT activity, azathioprine should be initiated at a low dose and titrated to 1.25 mg/kg and mercaptopurine should be initiated at a low dose and titrated to 0.75 mg/kg. Based on these titration goals, if the targeted full dose for mercaptopurine is 1 mg/kg, then a dose reduction of approximately 30% would be more appropriate. If the targeted full dose is 1.5 mg/kg, a dose reduction of approximately 50% would be more appropriate. Thiopurine doses should be titrated based on response and disease-specific guidelines, allowing 2 to 4 weeks to reach steady state before dose titration.

For those with low TPMT activity, alternative therapy should be considered for nonmalignant conditions because of the risk of severe myelosuppression. For malignancy, or if a thiopurine is warranted for a nonmalignant condition, consider a 90% dose reduction and give the drug three times per week instead of daily. For example, acute lymphoblastic leukemia patients with low TPMT activity can be started on mercaptopurine 10 mg/m² three times per week instead of the usual starting dose.¹⁰ Thiopurine doses should be titrated based on response and disease-specific guidelines, allowing 4 to 6 weeks to reach steady state before dose titration.

RECOMMENDATIONS

Individuals with intermediate or low TPMT activity have an increased risk of myelosuppression. Because of the elevated risk for morbidity and death, especially for patients with low TPMT activity, multiple guidelines and regulatory agencies recommend TPMT genotyping or phenotyping if a thiopurine is prescribed.^25,28–32 Although additional cost-benefit analysis studies are needed, evidence suggests testing for TPMT activity may be cheaper than the costs associated with treating myelosuppression.

In view of treatment guidelines, the recommendations of regulatory agencies, cost-benefit analyses, and the availability of gene-based dosing recommendations, we consider the benefits of testing for TPMT activity to greatly outweigh any associated risks. Therefore, we recommend that TPMT testing be strongly considered before initiating therapy with a thiopurine.

The thiopurines azathioprine, mercaptopurine, and thioguanine are prodrugs that are converted to active thioguanine nucleotide metabolites or methylated by thiopurine methyltransferase (TPMT) to compounds with less pharmacologic activity. In the absence of TPMT activity, patients are likely to have higher concentrations of thioguanine nucleotides, which can pose an increased risk of severe life-threatening myelosuppression. Determining TPMT activity, either directly by phenotyping or indirectly by determining the specific genetic allele (different alleles have different enzymatic activity), can help identify patients at greater risk of severe myelosuppression. Therefore, we recommend that TPMT testing be strongly considered before initiating therapy with a thiopurine.

THIOPURINES AND TPMT

Azathioprine, mercaptopurine, and thioguanine are used for treating autoimmune and inflammatory diseases^1–3 and certain types of cancer such as leukemias and lymphomas.^1,4–6 Typically, azathioprine is used to treat nonmalignant conditions, thioguanine is used to treat malignancies, and mercaptopurine can be used to treat both malignant and nonmalignant conditions.

Although the exact mechanism of action of these drugs has not been completely elucidated, the active thioguanine nucleotide metabolites are thought to be incorporated into the DNA of leukocytes, resulting in DNA damage that subsequently leads to cell death and myelosuppression.^7–9

Variants of the TPMT gene may alter the activity of the TPMT enzyme, resulting in individual variability in thiopurine metabolism. Compared with people with normal (high) TPMT activity, those with intermediate or low TPMT activity metabolize the drugs more slowly, and are likely to have higher thioguanine nucleotide concentrations and therefore an increased risk of myelosuppression.

One of the earliest correlations between TPMT activity and thiopurine-induced myelosuppression was described in a pediatric patient with acute lymphocytic leukemia.¹⁰ After being prescribed a conventional mercaptopurine dosage (75 mg/m² daily), the patient developed severe myelosuppression and was observed to have a thioguanine nucleotide metabolite concentration seven times the observed population median. TPMT phenotyping demonstrated that the patient had low TPMT activity. Reducing the mercaptopurine dose by approximately 90% resulted in normalization of thioguanine nucleotide metabolite concentrations, and the myelosuppression subsequently resolved.

Approximately 10% of the population has intermediate TPMT activity and 0.3% has low or absent TPMT activity, though these percentages vary depending on ancestry.¹ Research has demonstrated that approximately 30% to 60% of those with intermediate TPMT activity cannot tolerate a full thiopurine dose (eg, azathioprine 2–3 mg/kg/day or mercaptopurine 1.5 mg/kg/day).¹ Almost all patients with low TPMT activity will develop life-threating myelosuppression if prescribed a full thiopurine dose.¹

SHOULD TPMT ACTIVITY BE DETERMINED FOR EVERY PATIENT PRESCRIBED A THIOPURINE?

Although determining TPMT activity in thiopurine-naïve patients will assist clinicians in selecting a thiopurine starting dose or in deciding if an alternative agent is warranted, there are instances when a clinician may elect to not perform a TPMT genotype or phenotype test. For example, determining TPMT activity is not recommended for patients who previously tolerated thiopurine therapy at full steady-state doses.

The required starting dose of a thiopurine can influence the decision on whether or not to test for TPMT activity. TPMT genotyping or phenotyping may be of most benefit for patients requiring immediate full doses of a thiopurine.¹¹ Ideally, TPMT activity should be determined before prescribing immediate full doses of a thiopurine. This could be achieved by preemptively ordering a TPMT test in patients likely to require immunosuppression—for example, in patients diagnosed with inflammatory or autoimmune diseases. If therapy cannot be delayed and TPMT activity is unknown, ordering a TPMT test at the time of prescribing a full thiopurine dose is still of benefit. Depending on the clinical laboratory utilized for testing, TPMT phenotype results are usually reported in 3 to 5 days, and TPMT genotype results are usually reported in 5 to 7 days. Because most patients will not reach steady-state concentrations for 2 to 6 weeks, clinicians could initiate immediate full doses of a thiopurine and modify therapy based on TPMT test results before accumulation of thioguanine nucleotide metabolites occurs. Caution should be used with this approach, particularly in situations where the clinical laboratory may not return results in a timely manner.

For patients who are candidates for an initial low dose of a thiopurine, clinicians may choose to slowly titrate doses based on response and tolerability instead of determining TPMT activity.¹¹ Depending on the starting dose and how slowly titration occurs, initiating a thiopurine at a low dose and titrating based on response can be a feasible approach for patients with intermediate TPMT activity. Because drastic thiopurine dose reductions of approximately 10-fold are required for patients with low TPMT activity, which is a much smaller dosage than most clinicians will initially prescribe, the starting dosage will likely not be low enough to prevent myelosuppression in patients with low TPMT activity.^1,10

Determining TPMT activity can help clinicians establish an appropriate titration schedule. Patients with normal TPMT activity will usually reach thiopurine steady-state concentrations in 2 weeks, and the dosage can be titrated based on response.¹ Alterations in TPMT activity influence the pharmacokinetic parameters of thiopurines, and the time to reach steady-state is extended to 4 or 6 weeks for those with intermediate or low TPMT activity.¹ Increasing the thiopurine dosage before reaching steady state can lead to the prescribing of doses that will not be tolerated, resulting in myelosuppression.

Factors to consider when deciding if TPMT activity should be assessed include the disease state being treated and corresponding starting dose, the need for immediate full doses, and previous documented tolerance of thiopurines at steady-state doses. As with many aspects of medicine that have multiple options, coupled with an increase in patient access to healthcare information, the decision to test for TPMT activity may include shared decision-making between patients and providers. Although TPMT genotyping or phenotyping can help identify those at greatest risk of severe myelosuppression, such assays do not replace routine monitoring for myelosuppression, hepatotoxicity, or pancreatitis that may be caused by thiopurines.

WHAT TESTS ARE AVAILABLE TO DETERMINE TPMT ACTIVITY?

Patients with intermediate or low TPMT activity can be identified by either genotyping or phenotyping. There are considerations, though, that clinicians should be aware of before selecting a particular test.

TPMT genotyping

Four TPMT alleles, TPMT*2, *3A, *3B, and *3C, account for over 90% of inactivating polymorphisms.¹² Therefore, most reference laboratories only analyze for those genetic variants. Based on the reported test result, a predicted phenotype (eg, normal, intermediate, or low TPMT activity) can be assigned. Table 1 lists the predicted phenotypes for select genotyping results.

TPMT phenotyping

Phenotyping quantitates TPMT enzyme activity in erythrocytes, and based on the result, patients are classified as having normal, intermediate, or low TPMT activity. Because internal standards and other testing conditions may differ between reference laboratories, test results must be interpreted in the context of the laboratory that performed the assay.

Which test is right for my patient?

In most cases, either the genotype or the phenotype test provides sufficient information to guide thiopurine therapy. There are certain circumstances, though, in which the genotype or phenotype test is less informative.

TPMT genotyping, when performed using a blood specimen, is not recommended in those with a history of allogeneic bone marrow transplantation, as the result would reflect the donor’s genotype, not the patient’s. In such instances, monitoring of white blood cell counts and thiopurine metabolites may be more beneficial.

TPMT phenotyping may be inaccurate if performed within 30 to 90 days of an erythrocyte transfusion, as the test result may be influenced by donor erythrocytes. If a patient is receiving erythrocyte transfusions, TPMT genotyping is preferable to phenotyping.

Test cost may also be a consideration when determining if the genotype or phenotype test is best for your patient. Costs vary by laboratory, but phenotyping is generally less expensive than genotyping. The cost of genotyping, though, continues to decrease.¹³ The approximate commercial cost is $200 for phenotyping and $450 for genotyping, but laboratory fees may be substantially higher. Several insurance plans, including Medicare, cover TPMT testing, but reimbursement and copayments vary, depending on the patient’s specific plan.

There are conflicting data as to whether determining TPMT status is^11,14–18 or is not¹⁹ cost-effective. Multiple studies suggest that the cost of genotyping a sufficient number of patients to identify a single individual at high risk of myelosuppression is cheaper than the costs associated with treating an adverse event. Additional cost-benefit studies are needed, particularly studies that consider how bundled payments and outcomes-based reimbursement influence cost-effectiveness.

MODIFYING THIOPURINE THERAPY BASED ON TPMT ACTIVITY

There is a strong correlation between TPMT activity and tolerated thiopurine doses, with those having intermediate or low TPMT activity requiring lower doses.^10,20–23 Adjusting mercaptopurine doses based on TPMT activity to prevent hematopoietic toxicity has been successfully demonstrated in pediatric patients with acute lymphoblastic leukemia.²⁴ Furthermore, reducing initial thiopurine doses to avoid myelosuppression and titrating based on response has been shown to not compromise outcomes.^1,25,26 The Clinical Pharmacogenetic Implementation Consortium (CPIC) has developed an evidence-based guideline on how to adjust thiopurine doses based on TPMT activity,¹ summarized in Table 2. These dosing recommendations are classified as “strong.”

Patients with normal TPMT activity should be prescribed the usual thiopurine starting dose as indicated by disease-specific guidelines.

For those with intermediate TPMT activity, the CPIC guideline recommends reducing the initial targeted full dose of azathioprine and mercaptopurine by 30% to 70% and reducing the targeted full dose of thioguanine by 30% to 50%. The percentage of dose reduction depends on the targeted full dose. Siegel and Sands²⁷ suggested that for those who are diagnosed with inflammatory bowel disease and have intermediate TPMT activity, azathioprine should be initiated at a low dose and titrated to 1.25 mg/kg and mercaptopurine should be initiated at a low dose and titrated to 0.75 mg/kg. Based on these titration goals, if the targeted full dose for mercaptopurine is 1 mg/kg, then a dose reduction of approximately 30% would be more appropriate. If the targeted full dose is 1.5 mg/kg, a dose reduction of approximately 50% would be more appropriate. Thiopurine doses should be titrated based on response and disease-specific guidelines, allowing 2 to 4 weeks to reach steady state before dose titration.

For those with low TPMT activity, alternative therapy should be considered for nonmalignant conditions because of the risk of severe myelosuppression. For malignancy, or if a thiopurine is warranted for a nonmalignant condition, consider a 90% dose reduction and give the drug three times per week instead of daily. For example, acute lymphoblastic leukemia patients with low TPMT activity can be started on mercaptopurine 10 mg/m² three times per week instead of the usual starting dose.¹⁰ Thiopurine doses should be titrated based on response and disease-specific guidelines, allowing 4 to 6 weeks to reach steady state before dose titration.

RECOMMENDATIONS

Individuals with intermediate or low TPMT activity have an increased risk of myelosuppression. Because of the elevated risk for morbidity and death, especially for patients with low TPMT activity, multiple guidelines and regulatory agencies recommend TPMT genotyping or phenotyping if a thiopurine is prescribed.^25,28–32 Although additional cost-benefit analysis studies are needed, evidence suggests testing for TPMT activity may be cheaper than the costs associated with treating myelosuppression.

In view of treatment guidelines, the recommendations of regulatory agencies, cost-benefit analyses, and the availability of gene-based dosing recommendations, we consider the benefits of testing for TPMT activity to greatly outweigh any associated risks. Therefore, we recommend that TPMT testing be strongly considered before initiating therapy with a thiopurine.

The thiopurines azathioprine, mercaptopurine, and thioguanine are prodrugs that are converted to active thioguanine nucleotide metabolites or methylated by thiopurine methyltransferase (TPMT) to compounds with less pharmacologic activity. In the absence of TPMT activity, patients are likely to have higher concentrations of thioguanine nucleotides, which can pose an increased risk of severe life-threatening myelosuppression. Determining TPMT activity, either directly by phenotyping or indirectly by determining the specific genetic allele (different alleles have different enzymatic activity), can help identify patients at greater risk of severe myelosuppression. Therefore, we recommend that TPMT testing be strongly considered before initiating therapy with a thiopurine.

THIOPURINES AND TPMT

Azathioprine, mercaptopurine, and thioguanine are used for treating autoimmune and inflammatory diseases^1–3 and certain types of cancer such as leukemias and lymphomas.^1,4–6 Typically, azathioprine is used to treat nonmalignant conditions, thioguanine is used to treat malignancies, and mercaptopurine can be used to treat both malignant and nonmalignant conditions.

Although the exact mechanism of action of these drugs has not been completely elucidated, the active thioguanine nucleotide metabolites are thought to be incorporated into the DNA of leukocytes, resulting in DNA damage that subsequently leads to cell death and myelosuppression.^7–9

Variants of the TPMT gene may alter the activity of the TPMT enzyme, resulting in individual variability in thiopurine metabolism. Compared with people with normal (high) TPMT activity, those with intermediate or low TPMT activity metabolize the drugs more slowly, and are likely to have higher thioguanine nucleotide concentrations and therefore an increased risk of myelosuppression.

One of the earliest correlations between TPMT activity and thiopurine-induced myelosuppression was described in a pediatric patient with acute lymphocytic leukemia.¹⁰ After being prescribed a conventional mercaptopurine dosage (75 mg/m² daily), the patient developed severe myelosuppression and was observed to have a thioguanine nucleotide metabolite concentration seven times the observed population median. TPMT phenotyping demonstrated that the patient had low TPMT activity. Reducing the mercaptopurine dose by approximately 90% resulted in normalization of thioguanine nucleotide metabolite concentrations, and the myelosuppression subsequently resolved.

Approximately 10% of the population has intermediate TPMT activity and 0.3% has low or absent TPMT activity, though these percentages vary depending on ancestry.¹ Research has demonstrated that approximately 30% to 60% of those with intermediate TPMT activity cannot tolerate a full thiopurine dose (eg, azathioprine 2–3 mg/kg/day or mercaptopurine 1.5 mg/kg/day).¹ Almost all patients with low TPMT activity will develop life-threating myelosuppression if prescribed a full thiopurine dose.¹

SHOULD TPMT ACTIVITY BE DETERMINED FOR EVERY PATIENT PRESCRIBED A THIOPURINE?

Although determining TPMT activity in thiopurine-naïve patients will assist clinicians in selecting a thiopurine starting dose or in deciding if an alternative agent is warranted, there are instances when a clinician may elect to not perform a TPMT genotype or phenotype test. For example, determining TPMT activity is not recommended for patients who previously tolerated thiopurine therapy at full steady-state doses.

The required starting dose of a thiopurine can influence the decision on whether or not to test for TPMT activity. TPMT genotyping or phenotyping may be of most benefit for patients requiring immediate full doses of a thiopurine.¹¹ Ideally, TPMT activity should be determined before prescribing immediate full doses of a thiopurine. This could be achieved by preemptively ordering a TPMT test in patients likely to require immunosuppression—for example, in patients diagnosed with inflammatory or autoimmune diseases. If therapy cannot be delayed and TPMT activity is unknown, ordering a TPMT test at the time of prescribing a full thiopurine dose is still of benefit. Depending on the clinical laboratory utilized for testing, TPMT phenotype results are usually reported in 3 to 5 days, and TPMT genotype results are usually reported in 5 to 7 days. Because most patients will not reach steady-state concentrations for 2 to 6 weeks, clinicians could initiate immediate full doses of a thiopurine and modify therapy based on TPMT test results before accumulation of thioguanine nucleotide metabolites occurs. Caution should be used with this approach, particularly in situations where the clinical laboratory may not return results in a timely manner.

For patients who are candidates for an initial low dose of a thiopurine, clinicians may choose to slowly titrate doses based on response and tolerability instead of determining TPMT activity.¹¹ Depending on the starting dose and how slowly titration occurs, initiating a thiopurine at a low dose and titrating based on response can be a feasible approach for patients with intermediate TPMT activity. Because drastic thiopurine dose reductions of approximately 10-fold are required for patients with low TPMT activity, which is a much smaller dosage than most clinicians will initially prescribe, the starting dosage will likely not be low enough to prevent myelosuppression in patients with low TPMT activity.^1,10

Determining TPMT activity can help clinicians establish an appropriate titration schedule. Patients with normal TPMT activity will usually reach thiopurine steady-state concentrations in 2 weeks, and the dosage can be titrated based on response.¹ Alterations in TPMT activity influence the pharmacokinetic parameters of thiopurines, and the time to reach steady-state is extended to 4 or 6 weeks for those with intermediate or low TPMT activity.¹ Increasing the thiopurine dosage before reaching steady state can lead to the prescribing of doses that will not be tolerated, resulting in myelosuppression.

Factors to consider when deciding if TPMT activity should be assessed include the disease state being treated and corresponding starting dose, the need for immediate full doses, and previous documented tolerance of thiopurines at steady-state doses. As with many aspects of medicine that have multiple options, coupled with an increase in patient access to healthcare information, the decision to test for TPMT activity may include shared decision-making between patients and providers. Although TPMT genotyping or phenotyping can help identify those at greatest risk of severe myelosuppression, such assays do not replace routine monitoring for myelosuppression, hepatotoxicity, or pancreatitis that may be caused by thiopurines.

WHAT TESTS ARE AVAILABLE TO DETERMINE TPMT ACTIVITY?

Patients with intermediate or low TPMT activity can be identified by either genotyping or phenotyping. There are considerations, though, that clinicians should be aware of before selecting a particular test.

TPMT genotyping

Four TPMT alleles, TPMT*2, *3A, *3B, and *3C, account for over 90% of inactivating polymorphisms.¹² Therefore, most reference laboratories only analyze for those genetic variants. Based on the reported test result, a predicted phenotype (eg, normal, intermediate, or low TPMT activity) can be assigned. Table 1 lists the predicted phenotypes for select genotyping results.

TPMT phenotyping

Phenotyping quantitates TPMT enzyme activity in erythrocytes, and based on the result, patients are classified as having normal, intermediate, or low TPMT activity. Because internal standards and other testing conditions may differ between reference laboratories, test results must be interpreted in the context of the laboratory that performed the assay.

Which test is right for my patient?

In most cases, either the genotype or the phenotype test provides sufficient information to guide thiopurine therapy. There are certain circumstances, though, in which the genotype or phenotype test is less informative.

TPMT genotyping, when performed using a blood specimen, is not recommended in those with a history of allogeneic bone marrow transplantation, as the result would reflect the donor’s genotype, not the patient’s. In such instances, monitoring of white blood cell counts and thiopurine metabolites may be more beneficial.

TPMT phenotyping may be inaccurate if performed within 30 to 90 days of an erythrocyte transfusion, as the test result may be influenced by donor erythrocytes. If a patient is receiving erythrocyte transfusions, TPMT genotyping is preferable to phenotyping.

Test cost may also be a consideration when determining if the genotype or phenotype test is best for your patient. Costs vary by laboratory, but phenotyping is generally less expensive than genotyping. The cost of genotyping, though, continues to decrease.¹³ The approximate commercial cost is $200 for phenotyping and $450 for genotyping, but laboratory fees may be substantially higher. Several insurance plans, including Medicare, cover TPMT testing, but reimbursement and copayments vary, depending on the patient’s specific plan.

There are conflicting data as to whether determining TPMT status is^11,14–18 or is not¹⁹ cost-effective. Multiple studies suggest that the cost of genotyping a sufficient number of patients to identify a single individual at high risk of myelosuppression is cheaper than the costs associated with treating an adverse event. Additional cost-benefit studies are needed, particularly studies that consider how bundled payments and outcomes-based reimbursement influence cost-effectiveness.

MODIFYING THIOPURINE THERAPY BASED ON TPMT ACTIVITY

There is a strong correlation between TPMT activity and tolerated thiopurine doses, with those having intermediate or low TPMT activity requiring lower doses.^10,20–23 Adjusting mercaptopurine doses based on TPMT activity to prevent hematopoietic toxicity has been successfully demonstrated in pediatric patients with acute lymphoblastic leukemia.²⁴ Furthermore, reducing initial thiopurine doses to avoid myelosuppression and titrating based on response has been shown to not compromise outcomes.^1,25,26 The Clinical Pharmacogenetic Implementation Consortium (CPIC) has developed an evidence-based guideline on how to adjust thiopurine doses based on TPMT activity,¹ summarized in Table 2. These dosing recommendations are classified as “strong.”

Patients with normal TPMT activity should be prescribed the usual thiopurine starting dose as indicated by disease-specific guidelines.

For those with intermediate TPMT activity, the CPIC guideline recommends reducing the initial targeted full dose of azathioprine and mercaptopurine by 30% to 70% and reducing the targeted full dose of thioguanine by 30% to 50%. The percentage of dose reduction depends on the targeted full dose. Siegel and Sands²⁷ suggested that for those who are diagnosed with inflammatory bowel disease and have intermediate TPMT activity, azathioprine should be initiated at a low dose and titrated to 1.25 mg/kg and mercaptopurine should be initiated at a low dose and titrated to 0.75 mg/kg. Based on these titration goals, if the targeted full dose for mercaptopurine is 1 mg/kg, then a dose reduction of approximately 30% would be more appropriate. If the targeted full dose is 1.5 mg/kg, a dose reduction of approximately 50% would be more appropriate. Thiopurine doses should be titrated based on response and disease-specific guidelines, allowing 2 to 4 weeks to reach steady state before dose titration.

For those with low TPMT activity, alternative therapy should be considered for nonmalignant conditions because of the risk of severe myelosuppression. For malignancy, or if a thiopurine is warranted for a nonmalignant condition, consider a 90% dose reduction and give the drug three times per week instead of daily. For example, acute lymphoblastic leukemia patients with low TPMT activity can be started on mercaptopurine 10 mg/m² three times per week instead of the usual starting dose.¹⁰ Thiopurine doses should be titrated based on response and disease-specific guidelines, allowing 4 to 6 weeks to reach steady state before dose titration.

RECOMMENDATIONS

Individuals with intermediate or low TPMT activity have an increased risk of myelosuppression. Because of the elevated risk for morbidity and death, especially for patients with low TPMT activity, multiple guidelines and regulatory agencies recommend TPMT genotyping or phenotyping if a thiopurine is prescribed.^25,28–32 Although additional cost-benefit analysis studies are needed, evidence suggests testing for TPMT activity may be cheaper than the costs associated with treating myelosuppression.

In view of treatment guidelines, the recommendations of regulatory agencies, cost-benefit analyses, and the availability of gene-based dosing recommendations, we consider the benefits of testing for TPMT activity to greatly outweigh any associated risks. Therefore, we recommend that TPMT testing be strongly considered before initiating therapy with a thiopurine.

To the Editor: We read the review on enterovirus D68¹ (EV-D68) with great interest, and we thought it merited comment.

During the current influenza season, we have had several adult cases of EV-D68 presenting as an influenza-like illness. EV-D68 was diagnosed by nasal swab viral film array polymerase chain reaction (PCR) testing. We agree with the authors that the clinical spectrum of enteroviral infection includes a variety of extraintestinal manifestations, eg, acute pancreatitis. As more cases of EV-D68 are described, the range of clinical manifestations will be increased.^2–5

We recently saw a 27-year-old woman who presented with an influenza-like illness, but with a main complaint of right-upper-quadrant abdominal pain. She denied recent travel or contacts with sick children or adults. Her past medical history was unremarkable, and she was not taking any medications. The physical examination was unremarkable except for moderately severe tenderness in the right upper quadrant, with no rebound or guarding.

Results of laboratory testing at hospital admission included a white blood cell count of 7.3 × 10⁹/L (49% neutrophils, 41% lymphocytes, 7% monocytes, 3% eosinophils), a normal platelet count, serum lipase 73 U/L (reference range 5.6–51.3 U/L), and serum amylase 211 U/L (37–121 U/L). Serum aminotransferase and alkaline phosphatase levels were normal. Abdominal ultrasonography was unremarkable. Nasal swab for multiplex PCR testing for respiratory viruses was positive for human rhinovirus-enterovirus. Further PCR testing was positive for EV-D68 (New York State Department of Health, Wadsworth Laboratory). Her abdominal pain was treated symptomatically; she gradually improved and was discharged.

This instance of EV-D68 in a healthy 27-year-old woman presenting with influenza-like illness and acute pain in the right upper quadrant is the first we have seen of EV-D68 presenting as acute pancreatitis. Clinicians should be aware that EV-D68, like influenza, may present with gastrointestinal manifestations.

To the Editor: We read the review on enterovirus D68¹ (EV-D68) with great interest, and we thought it merited comment.

During the current influenza season, we have had several adult cases of EV-D68 presenting as an influenza-like illness. EV-D68 was diagnosed by nasal swab viral film array polymerase chain reaction (PCR) testing. We agree with the authors that the clinical spectrum of enteroviral infection includes a variety of extraintestinal manifestations, eg, acute pancreatitis. As more cases of EV-D68 are described, the range of clinical manifestations will be increased.^2–5

We recently saw a 27-year-old woman who presented with an influenza-like illness, but with a main complaint of right-upper-quadrant abdominal pain. She denied recent travel or contacts with sick children or adults. Her past medical history was unremarkable, and she was not taking any medications. The physical examination was unremarkable except for moderately severe tenderness in the right upper quadrant, with no rebound or guarding.

Results of laboratory testing at hospital admission included a white blood cell count of 7.3 × 10⁹/L (49% neutrophils, 41% lymphocytes, 7% monocytes, 3% eosinophils), a normal platelet count, serum lipase 73 U/L (reference range 5.6–51.3 U/L), and serum amylase 211 U/L (37–121 U/L). Serum aminotransferase and alkaline phosphatase levels were normal. Abdominal ultrasonography was unremarkable. Nasal swab for multiplex PCR testing for respiratory viruses was positive for human rhinovirus-enterovirus. Further PCR testing was positive for EV-D68 (New York State Department of Health, Wadsworth Laboratory). Her abdominal pain was treated symptomatically; she gradually improved and was discharged.

This instance of EV-D68 in a healthy 27-year-old woman presenting with influenza-like illness and acute pain in the right upper quadrant is the first we have seen of EV-D68 presenting as acute pancreatitis. Clinicians should be aware that EV-D68, like influenza, may present with gastrointestinal manifestations.

To the Editor: We read the review on enterovirus D68¹ (EV-D68) with great interest, and we thought it merited comment.

During the current influenza season, we have had several adult cases of EV-D68 presenting as an influenza-like illness. EV-D68 was diagnosed by nasal swab viral film array polymerase chain reaction (PCR) testing. We agree with the authors that the clinical spectrum of enteroviral infection includes a variety of extraintestinal manifestations, eg, acute pancreatitis. As more cases of EV-D68 are described, the range of clinical manifestations will be increased.^2–5

We recently saw a 27-year-old woman who presented with an influenza-like illness, but with a main complaint of right-upper-quadrant abdominal pain. She denied recent travel or contacts with sick children or adults. Her past medical history was unremarkable, and she was not taking any medications. The physical examination was unremarkable except for moderately severe tenderness in the right upper quadrant, with no rebound or guarding.

Results of laboratory testing at hospital admission included a white blood cell count of 7.3 × 10⁹/L (49% neutrophils, 41% lymphocytes, 7% monocytes, 3% eosinophils), a normal platelet count, serum lipase 73 U/L (reference range 5.6–51.3 U/L), and serum amylase 211 U/L (37–121 U/L). Serum aminotransferase and alkaline phosphatase levels were normal. Abdominal ultrasonography was unremarkable. Nasal swab for multiplex PCR testing for respiratory viruses was positive for human rhinovirus-enterovirus. Further PCR testing was positive for EV-D68 (New York State Department of Health, Wadsworth Laboratory). Her abdominal pain was treated symptomatically; she gradually improved and was discharged.

This instance of EV-D68 in a healthy 27-year-old woman presenting with influenza-like illness and acute pain in the right upper quadrant is the first we have seen of EV-D68 presenting as acute pancreatitis. Clinicians should be aware that EV-D68, like influenza, may present with gastrointestinal manifestations.

To the Editor: In the February 2015 issue of Cleveland Clinic Journal of Medicine, Dr. David A. Katzka reviewed the major clinical features of eosinophilic esophagitis and, having presented its allergic component, rightly assessed the inherent difficulties of detecting and eliminating food allergens involved in the development and course of this disease.¹ The inadequacies of serologic testing were mentioned, as well as the difficulties of endoscopy and biopsy “painstakingly performed with the removal and reintroduction of every suspected food allergen, requiring multiple biopsies weekly, which is impractical for safety and economic reasons.”¹

In a meta-analysis, Arias et al² showed that such an individualized approach for each food is not really necessary. Elemental diets with graded reintroduction of grouped foods were effective in detecting and treating the responsible food allergies in 90.8% of cases (95% confidence interval [CI] 84.7–95.5). In fact, the more pragmatic, simple, and inexpensive six-food-elimination diet was also reasonably effective (72.1% of cases, 95% CI 65.8–78.1). Both outcomes are far superior to elimination strategies directed at immunoglobulin E (IgE), which were effective in only 45.5% of cases (95% CI 35.4–55.7%).²

Franciosi and Liacouras³ described a practical and comprehensive elimination-reintroduction protocol consisting of four steps that, in combination with symptom diaries, can easily identify responsible foods.

In our practice, graded elimination-reintroduction diets—which, depending on history, may range from the basic six-food-elimination diet to the fully developed Franciosi-Liacouras protocol—along with food IgE testing and judicial use of IgG testing against selected foods, have yielded detection and successful treatment rates comparable to the 90.8% rate reported by Arias et al.² Upon identification of food allergens, a dual approach of diet restrictions and food immunotherapy is initiated. As a result of this approach, patients only need to undergo a single endoscopy and biopsy to demonstrate decreased eosinophil counts, usually 1 year after initiation of allergy treatment.

Of course, pharmacologic management is necessary in the treatment of eosinophilic esophagitis. However, the inclusion of montelukast in the standard first-line regimen for eosinophilic esophagitis is not yet a firmly established practice. Not all eosinophilia can be equated to allergy, and not all allergic inflammation is leukotriene-dependent. Furthermore, too little is known about the secondary effects of leukotrienes on immune regulation and whether their blockade is really desirable in eosinophilic esophagitis. But it is known that leukotriene receptor antagonists, especially montelukast, can trigger Churg-Strauss vasculitis, a syndrome whose eosinophil activation, homing pattern, and subsequent proliferation—as well as its exclusive prevalence in allergic patients with asthma and chronic sinusitis—bear some similarity to those of eosinophilic esophagitis.

To the Editor: In the February 2015 issue of Cleveland Clinic Journal of Medicine, Dr. David A. Katzka reviewed the major clinical features of eosinophilic esophagitis and, having presented its allergic component, rightly assessed the inherent difficulties of detecting and eliminating food allergens involved in the development and course of this disease.¹ The inadequacies of serologic testing were mentioned, as well as the difficulties of endoscopy and biopsy “painstakingly performed with the removal and reintroduction of every suspected food allergen, requiring multiple biopsies weekly, which is impractical for safety and economic reasons.”¹

In a meta-analysis, Arias et al² showed that such an individualized approach for each food is not really necessary. Elemental diets with graded reintroduction of grouped foods were effective in detecting and treating the responsible food allergies in 90.8% of cases (95% confidence interval [CI] 84.7–95.5). In fact, the more pragmatic, simple, and inexpensive six-food-elimination diet was also reasonably effective (72.1% of cases, 95% CI 65.8–78.1). Both outcomes are far superior to elimination strategies directed at immunoglobulin E (IgE), which were effective in only 45.5% of cases (95% CI 35.4–55.7%).²

Franciosi and Liacouras³ described a practical and comprehensive elimination-reintroduction protocol consisting of four steps that, in combination with symptom diaries, can easily identify responsible foods.

In our practice, graded elimination-reintroduction diets—which, depending on history, may range from the basic six-food-elimination diet to the fully developed Franciosi-Liacouras protocol—along with food IgE testing and judicial use of IgG testing against selected foods, have yielded detection and successful treatment rates comparable to the 90.8% rate reported by Arias et al.² Upon identification of food allergens, a dual approach of diet restrictions and food immunotherapy is initiated. As a result of this approach, patients only need to undergo a single endoscopy and biopsy to demonstrate decreased eosinophil counts, usually 1 year after initiation of allergy treatment.

Of course, pharmacologic management is necessary in the treatment of eosinophilic esophagitis. However, the inclusion of montelukast in the standard first-line regimen for eosinophilic esophagitis is not yet a firmly established practice. Not all eosinophilia can be equated to allergy, and not all allergic inflammation is leukotriene-dependent. Furthermore, too little is known about the secondary effects of leukotrienes on immune regulation and whether their blockade is really desirable in eosinophilic esophagitis. But it is known that leukotriene receptor antagonists, especially montelukast, can trigger Churg-Strauss vasculitis, a syndrome whose eosinophil activation, homing pattern, and subsequent proliferation—as well as its exclusive prevalence in allergic patients with asthma and chronic sinusitis—bear some similarity to those of eosinophilic esophagitis.

To the Editor: In the February 2015 issue of Cleveland Clinic Journal of Medicine, Dr. David A. Katzka reviewed the major clinical features of eosinophilic esophagitis and, having presented its allergic component, rightly assessed the inherent difficulties of detecting and eliminating food allergens involved in the development and course of this disease.¹ The inadequacies of serologic testing were mentioned, as well as the difficulties of endoscopy and biopsy “painstakingly performed with the removal and reintroduction of every suspected food allergen, requiring multiple biopsies weekly, which is impractical for safety and economic reasons.”¹

In a meta-analysis, Arias et al² showed that such an individualized approach for each food is not really necessary. Elemental diets with graded reintroduction of grouped foods were effective in detecting and treating the responsible food allergies in 90.8% of cases (95% confidence interval [CI] 84.7–95.5). In fact, the more pragmatic, simple, and inexpensive six-food-elimination diet was also reasonably effective (72.1% of cases, 95% CI 65.8–78.1). Both outcomes are far superior to elimination strategies directed at immunoglobulin E (IgE), which were effective in only 45.5% of cases (95% CI 35.4–55.7%).²

Franciosi and Liacouras³ described a practical and comprehensive elimination-reintroduction protocol consisting of four steps that, in combination with symptom diaries, can easily identify responsible foods.

In our practice, graded elimination-reintroduction diets—which, depending on history, may range from the basic six-food-elimination diet to the fully developed Franciosi-Liacouras protocol—along with food IgE testing and judicial use of IgG testing against selected foods, have yielded detection and successful treatment rates comparable to the 90.8% rate reported by Arias et al.² Upon identification of food allergens, a dual approach of diet restrictions and food immunotherapy is initiated. As a result of this approach, patients only need to undergo a single endoscopy and biopsy to demonstrate decreased eosinophil counts, usually 1 year after initiation of allergy treatment.

Of course, pharmacologic management is necessary in the treatment of eosinophilic esophagitis. However, the inclusion of montelukast in the standard first-line regimen for eosinophilic esophagitis is not yet a firmly established practice. Not all eosinophilia can be equated to allergy, and not all allergic inflammation is leukotriene-dependent. Furthermore, too little is known about the secondary effects of leukotrienes on immune regulation and whether their blockade is really desirable in eosinophilic esophagitis. But it is known that leukotriene receptor antagonists, especially montelukast, can trigger Churg-Strauss vasculitis, a syndrome whose eosinophil activation, homing pattern, and subsequent proliferation—as well as its exclusive prevalence in allergic patients with asthma and chronic sinusitis—bear some similarity to those of eosinophilic esophagitis.

In Reply: I am most grateful to Drs. Theodoropoulos and Morris for their letter. I fully agree that we are getting smarter with diet elimination therapies by introducing more than one food at a time in the hope that we can lessen the number of endoscopies needed to isolate specific antigenic causes of eosinophilic esophagitis. This is not always successful, but in some of the more fortunate patients, we can get by with one or two endoscopies. It is my hope that with less-invasive tools such as the Cytosponge, the esophageal string test, and perhaps even serum evaluations, we can further embrace diet therapy as a standard treatment in more patients with eosinophilic esophagitis.

I think it is also important to note that although traditional radioallergosorbent and skin testing was only 45% accurate for eosinophilic esophagitis in the meta-analysis cited, this testing is still important, given the number of IgE-related allergies additionally uncovered in patients with eosinophilic esophagitis.

In Reply: I am most grateful to Drs. Theodoropoulos and Morris for their letter. I fully agree that we are getting smarter with diet elimination therapies by introducing more than one food at a time in the hope that we can lessen the number of endoscopies needed to isolate specific antigenic causes of eosinophilic esophagitis. This is not always successful, but in some of the more fortunate patients, we can get by with one or two endoscopies. It is my hope that with less-invasive tools such as the Cytosponge, the esophageal string test, and perhaps even serum evaluations, we can further embrace diet therapy as a standard treatment in more patients with eosinophilic esophagitis.

I think it is also important to note that although traditional radioallergosorbent and skin testing was only 45% accurate for eosinophilic esophagitis in the meta-analysis cited, this testing is still important, given the number of IgE-related allergies additionally uncovered in patients with eosinophilic esophagitis.

In Reply: I am most grateful to Drs. Theodoropoulos and Morris for their letter. I fully agree that we are getting smarter with diet elimination therapies by introducing more than one food at a time in the hope that we can lessen the number of endoscopies needed to isolate specific antigenic causes of eosinophilic esophagitis. This is not always successful, but in some of the more fortunate patients, we can get by with one or two endoscopies. It is my hope that with less-invasive tools such as the Cytosponge, the esophageal string test, and perhaps even serum evaluations, we can further embrace diet therapy as a standard treatment in more patients with eosinophilic esophagitis.

I think it is also important to note that although traditional radioallergosorbent and skin testing was only 45% accurate for eosinophilic esophagitis in the meta-analysis cited, this testing is still important, given the number of IgE-related allergies additionally uncovered in patients with eosinophilic esophagitis.

To the Editor: In his article, Dr. Lehman¹ argued that because the Patient Protection and Affordable Care Act (PPACA) attempts to break the healthcare “iron triangle” by simultaneously improving access and quality while reducing costs, it may paradoxically make the situation worse on all three fronts. However, this line of argument fails to provide a comparison—that is, worse compared to what? While Dr. Lehman does not suggest a comparison, two come to mind that could be implied from his arguments: 1) doing nothing, or 2) targeting reform at only two sides of the triangle.

Prior to the PPACA, the US healthcare system had serious problems with access, quality, and cost.² While it is true that any reform could potentially be worse than doing nothing, none of the three seemed to be getting any better under the status quo. Both candidates for president in 2008 agreed that doing nothing was no longer an option.^3,4 Alternatively, trying to improve two legs of the triangle (say, access and quality) while acknowledging that the third (cost) would suffer would have been just as politically untenable.

The true explanation for how the PPACA could expect to (and may still) improve access and quality while reducing healthcare costs (compared to no reform) is that the PPACA is not a single intervention, as is obvious from the 2,000-plus pages of the law. No single component of the law needs to do all three. For example, expanding Medicaid improves access and quality (especially for those without prior coverage) but undoubtedly raises costs. On the other hand, accountable care organizations should decrease costs by incentivizing providers to be more efficient and reduce waste (and ideally would also improve quality).⁵ Given the low bar set prior to implementation of the PPACA, it was not a stretch to have expected any major reform to improve (not fix) our problems with access, quality, and cost.

To the Editor: In his article, Dr. Lehman¹ argued that because the Patient Protection and Affordable Care Act (PPACA) attempts to break the healthcare “iron triangle” by simultaneously improving access and quality while reducing costs, it may paradoxically make the situation worse on all three fronts. However, this line of argument fails to provide a comparison—that is, worse compared to what? While Dr. Lehman does not suggest a comparison, two come to mind that could be implied from his arguments: 1) doing nothing, or 2) targeting reform at only two sides of the triangle.

Prior to the PPACA, the US healthcare system had serious problems with access, quality, and cost.² While it is true that any reform could potentially be worse than doing nothing, none of the three seemed to be getting any better under the status quo. Both candidates for president in 2008 agreed that doing nothing was no longer an option.^3,4 Alternatively, trying to improve two legs of the triangle (say, access and quality) while acknowledging that the third (cost) would suffer would have been just as politically untenable.

The true explanation for how the PPACA could expect to (and may still) improve access and quality while reducing healthcare costs (compared to no reform) is that the PPACA is not a single intervention, as is obvious from the 2,000-plus pages of the law. No single component of the law needs to do all three. For example, expanding Medicaid improves access and quality (especially for those without prior coverage) but undoubtedly raises costs. On the other hand, accountable care organizations should decrease costs by incentivizing providers to be more efficient and reduce waste (and ideally would also improve quality).⁵ Given the low bar set prior to implementation of the PPACA, it was not a stretch to have expected any major reform to improve (not fix) our problems with access, quality, and cost.

To the Editor: In his article, Dr. Lehman¹ argued that because the Patient Protection and Affordable Care Act (PPACA) attempts to break the healthcare “iron triangle” by simultaneously improving access and quality while reducing costs, it may paradoxically make the situation worse on all three fronts. However, this line of argument fails to provide a comparison—that is, worse compared to what? While Dr. Lehman does not suggest a comparison, two come to mind that could be implied from his arguments: 1) doing nothing, or 2) targeting reform at only two sides of the triangle.

Prior to the PPACA, the US healthcare system had serious problems with access, quality, and cost.² While it is true that any reform could potentially be worse than doing nothing, none of the three seemed to be getting any better under the status quo. Both candidates for president in 2008 agreed that doing nothing was no longer an option.^3,4 Alternatively, trying to improve two legs of the triangle (say, access and quality) while acknowledging that the third (cost) would suffer would have been just as politically untenable.

The true explanation for how the PPACA could expect to (and may still) improve access and quality while reducing healthcare costs (compared to no reform) is that the PPACA is not a single intervention, as is obvious from the 2,000-plus pages of the law. No single component of the law needs to do all three. For example, expanding Medicaid improves access and quality (especially for those without prior coverage) but undoubtedly raises costs. On the other hand, accountable care organizations should decrease costs by incentivizing providers to be more efficient and reduce waste (and ideally would also improve quality).⁵ Given the low bar set prior to implementation of the PPACA, it was not a stretch to have expected any major reform to improve (not fix) our problems with access, quality, and cost.

In Reply: Many of the statements made by Dr. Riggs are indisputable. The conclusions drawn from these insights, however, are questionable.

The Patient Protection and Affordable Care Act (PPACA) was introduced under the premise that a patchwork of policies would improve access and quality of care while decreasing overall health expenditures. Dr. Riggs suggests that, since individual components are targeted toward some of these issues, the net effect of the PPACA is its breaking of the healthcare iron triangle.

Nothing could be further from the truth. This line of reasoning requires that the left hand knows not what the right hand is doing, and that each hand (ie, each component of the PPACA) can ignore the effects of the other, with each proclaiming success in its efforts. It is disingenuous to suggest that the PPACA, on the whole, improves upon the problems of access, quality, and cost if each of the program’s tenets addresses only one or two of the triangle’s vertices.

The PPACA suffers from its own lofty expectations. Rather than being a transformative law that shifts a paradigm, the PPACA is simply an evolution of an existing, broken system, cobbling together components everyone readily agrees are dysfunctional. It expands Medicaid, an insufficiently funded program for the most economically and medically disadvantaged Americans. It subsidizes private health insurance, which, for all its advantages, is likely responsible for the overconsumption of discounted healthcare. And it promotes the unproven concept of accountable care organizations, with no rational expectation that this approach would be superior to preferred provider organizations or health maintenance organizations. It is illogical to expect the sum of many broken parts to yield a superior outcome.

Dr. Riggs notes that trying to improve two legs of the triangle (increased access and improved quality) while acknowledging rising costs is politically untenable. On this point, he is absolutely correct. Discussing the harsh reality that healthcare is a scarce commodity is a political nonstarter. Until Americans demand—and politicians provide—difficult answers to the question of how we will provide healthcare in the 21st century, simultaneously improving delivery of care on all three fronts remains a fantasy. Barring truly transformative change, the iron triangle continues to rule the economics of American healthcare.

In Reply: Many of the statements made by Dr. Riggs are indisputable. The conclusions drawn from these insights, however, are questionable.

The Patient Protection and Affordable Care Act (PPACA) was introduced under the premise that a patchwork of policies would improve access and quality of care while decreasing overall health expenditures. Dr. Riggs suggests that, since individual components are targeted toward some of these issues, the net effect of the PPACA is its breaking of the healthcare iron triangle.

Nothing could be further from the truth. This line of reasoning requires that the left hand knows not what the right hand is doing, and that each hand (ie, each component of the PPACA) can ignore the effects of the other, with each proclaiming success in its efforts. It is disingenuous to suggest that the PPACA, on the whole, improves upon the problems of access, quality, and cost if each of the program’s tenets addresses only one or two of the triangle’s vertices.

The PPACA suffers from its own lofty expectations. Rather than being a transformative law that shifts a paradigm, the PPACA is simply an evolution of an existing, broken system, cobbling together components everyone readily agrees are dysfunctional. It expands Medicaid, an insufficiently funded program for the most economically and medically disadvantaged Americans. It subsidizes private health insurance, which, for all its advantages, is likely responsible for the overconsumption of discounted healthcare. And it promotes the unproven concept of accountable care organizations, with no rational expectation that this approach would be superior to preferred provider organizations or health maintenance organizations. It is illogical to expect the sum of many broken parts to yield a superior outcome.

Dr. Riggs notes that trying to improve two legs of the triangle (increased access and improved quality) while acknowledging rising costs is politically untenable. On this point, he is absolutely correct. Discussing the harsh reality that healthcare is a scarce commodity is a political nonstarter. Until Americans demand—and politicians provide—difficult answers to the question of how we will provide healthcare in the 21st century, simultaneously improving delivery of care on all three fronts remains a fantasy. Barring truly transformative change, the iron triangle continues to rule the economics of American healthcare.

In Reply: Many of the statements made by Dr. Riggs are indisputable. The conclusions drawn from these insights, however, are questionable.

The Patient Protection and Affordable Care Act (PPACA) was introduced under the premise that a patchwork of policies would improve access and quality of care while decreasing overall health expenditures. Dr. Riggs suggests that, since individual components are targeted toward some of these issues, the net effect of the PPACA is its breaking of the healthcare iron triangle.

Nothing could be further from the truth. This line of reasoning requires that the left hand knows not what the right hand is doing, and that each hand (ie, each component of the PPACA) can ignore the effects of the other, with each proclaiming success in its efforts. It is disingenuous to suggest that the PPACA, on the whole, improves upon the problems of access, quality, and cost if each of the program’s tenets addresses only one or two of the triangle’s vertices.

The PPACA suffers from its own lofty expectations. Rather than being a transformative law that shifts a paradigm, the PPACA is simply an evolution of an existing, broken system, cobbling together components everyone readily agrees are dysfunctional. It expands Medicaid, an insufficiently funded program for the most economically and medically disadvantaged Americans. It subsidizes private health insurance, which, for all its advantages, is likely responsible for the overconsumption of discounted healthcare. And it promotes the unproven concept of accountable care organizations, with no rational expectation that this approach would be superior to preferred provider organizations or health maintenance organizations. It is illogical to expect the sum of many broken parts to yield a superior outcome.

Dr. Riggs notes that trying to improve two legs of the triangle (increased access and improved quality) while acknowledging rising costs is politically untenable. On this point, he is absolutely correct. Discussing the harsh reality that healthcare is a scarce commodity is a political nonstarter. Until Americans demand—and politicians provide—difficult answers to the question of how we will provide healthcare in the 21st century, simultaneously improving delivery of care on all three fronts remains a fantasy. Barring truly transformative change, the iron triangle continues to rule the economics of American healthcare.

To the Editor: I read with keen interest the high-quality review of the pathogenesis, diagnosis, and management of alcoholic hepatitis by Dugum et al.¹ They clearly emphasized the high morbidity and mortality rates associated with this condition.

An important consideration for healthcare practitioners is that the presentation of alcoholic hepatitis can mimic an infectious process, eg, presenting with fever and an elevated white blood cell count. Indeed, clinicians should be vigilant and should routinely evaluate for an underlying infection in patients with suspected alcoholic hepatitis, because patients with liver disease are immunocompromised and several problems can potentially coexist in any given patient.

Therefore, clinicians should focus on the clinical history and examination (vital signs, mental status examination, presence of ascites) and should screen for common coinfections such as urinary tract infection and pneumonia with a white blood cell count with differential and other tests. Of particular importance, patients with ascites should undergo diagnostic abdominal paracentesis,² and empiric antimicrobial therapy for spontaneous bacterial peritonitis should be considered on a case-by-case basis.³

To the Editor: I read with keen interest the high-quality review of the pathogenesis, diagnosis, and management of alcoholic hepatitis by Dugum et al.¹ They clearly emphasized the high morbidity and mortality rates associated with this condition.

An important consideration for healthcare practitioners is that the presentation of alcoholic hepatitis can mimic an infectious process, eg, presenting with fever and an elevated white blood cell count. Indeed, clinicians should be vigilant and should routinely evaluate for an underlying infection in patients with suspected alcoholic hepatitis, because patients with liver disease are immunocompromised and several problems can potentially coexist in any given patient.

Therefore, clinicians should focus on the clinical history and examination (vital signs, mental status examination, presence of ascites) and should screen for common coinfections such as urinary tract infection and pneumonia with a white blood cell count with differential and other tests. Of particular importance, patients with ascites should undergo diagnostic abdominal paracentesis,² and empiric antimicrobial therapy for spontaneous bacterial peritonitis should be considered on a case-by-case basis.³

To the Editor: I read with keen interest the high-quality review of the pathogenesis, diagnosis, and management of alcoholic hepatitis by Dugum et al.¹ They clearly emphasized the high morbidity and mortality rates associated with this condition.

An important consideration for healthcare practitioners is that the presentation of alcoholic hepatitis can mimic an infectious process, eg, presenting with fever and an elevated white blood cell count. Indeed, clinicians should be vigilant and should routinely evaluate for an underlying infection in patients with suspected alcoholic hepatitis, because patients with liver disease are immunocompromised and several problems can potentially coexist in any given patient.

Therefore, clinicians should focus on the clinical history and examination (vital signs, mental status examination, presence of ascites) and should screen for common coinfections such as urinary tract infection and pneumonia with a white blood cell count with differential and other tests. Of particular importance, patients with ascites should undergo diagnostic abdominal paracentesis,² and empiric antimicrobial therapy for spontaneous bacterial peritonitis should be considered on a case-by-case basis.³