Guideline authors, AHA-ACC leaders confident in risk calculator



DALLAS – In the face of high-profile criticism of the new U.S. cholesterol-management guidelines released by the American College of Cardiology and American Heart Association on Nov. 12, the physicians who crafted the guidelines, as well as the leadership of the two organizations, stood firmly behind the work, reiterating that it is a big step forward in the battle against atherosclerotic cardiovascular disease.

During a last-minute press conference called on Monday morning, Nov. 18, to address concerns that first bubbled up over the prior weekend, a series of representatives from the guideline-writing panel stressed that the new cardiovascular-risk-calculation formula introduced in the guidelines reflected the best and most comprehensive evidence available today. They also stressed that the guidelines do not advocate simply using the formula and a rigid risk-threshold to decide whether or not a patient should receive a statin, but instead tell physicians and their patients to use the risk calculator as the starting point for a discussion of the risks and benefits that statin treatment might pose for each person.

"I think these are these are the most carefully vetted guidelines ever published," said Dr. Mariell Jessup, AHA president. "We’re confident that they are based on the best evidence."

"We intend to move forward with implementation of these guidelines," said Dr. Sidney Smith, professor of medicine at the University of North Carolina in Chapel Hill and chair of the ACC/AHA subcommittee on prevention guidelines.

The controversy began with an analysis run by two Harvard researchers starting on the day the guidelines and risk calculator came out that applied the new risk calculator to three databases at their immediate disposal, the Women’s Health Study, the Physicians’ Health Study, and the Women’s Health Initiative Observational Study. They found that the risk calculator overestimated the 10-year rate of atherosclerotic cardiovascular disease (ASCVD) event by 75%-150%, doubling the actual, observed risk in these three cohorts. The authors of the analysis, Dr. Paul M. Ridker and Nancy R. Cook, Sc.D., of Harvard Medical School and Brigham and Women’s Hospital, both in Boston, published their results in a brief article published online in the Lancet on Nov. 19.

Mitchel L. Zoler/IMNG Medical Media

Dr. Donald Lloyd-Jones

Based on their calculations, "it is possible that as many as 40% to 50% of the 33 million Americans targeted by the new guidelines for statin therapy do not actually have risk thresholds exceeding the 7.5% level suggested for treatment," the two researchers wrote. "Miscalibration to this extent should be reconciled and addressed ... before these new prediction models are widely implemented."

Their analysis was made available to the New York Times over the weekend, which led to a prominent story in the newspaper’s Nov. 18 edition that called this overestimate by the risk calculator a "major embarrassment," and quoted some prominent cardiologists who also called for a delay in implementation of the new guidelines and risk calculator.

The researchers who devised the calculator responded by acknowledging the flaws in the device, something they had already done in their manuscript, but stressed that it represented a major improvement over the risk calculator from the prior guidelines, the third edition of the Adult Treatment Panel (ATP III) used for the past 12 years, particularly because of its inclusion of strokes as a ASCVD endpoint and its reliance on databases that had substantial numbers of African Americans, two major features missing from ATP III.

A risk calculator "will never be perfect, but this is a huge step ahead from where we were 12 years ago," said Dr. Donald Lloyd-Jones, professor of preventive medicine at Northwestern University in Chicago and cochair of the panel that developed the risk calculator. "We made it better for women [by including stroke as an outcome], for African Americans, and for white men, too. We feel very confident that we are in a great place now, but as more data become available, we’re very happy to see if we can improve it further. You can certainly criticize the calculator, but I don’t know of anything that’s better," he said in an interview.

Other experts who led development of the new guidelines also stressed that they do not call for blindly prescribing a statin to every person whose risk calculates at or above 7.5%.

Mitchel L. Zoler/IMNG Medical Media

Dr. Neil Stone

"No one said that patients automatically get a statin. We said that there needs to be a risk discussion between the patient and physician, because sometimes the numbers make sense and sometimes they don’t," said Dr. Neil Stone, Robert Bonow Professor in the division of medicine-cardiology at Northwestern University and chair of the ACC/AHA panel that wrote the new guidelines. "For the first time, we built into the guidelines the unique judgment of physicians, and patients’ personal preferences." Risk calculation "is the start of a discussion" between a physician and patient, not the endpoint. He also noted that the guidelines included a built-in "buffer" because "we had evidence that statins are effective even for patients with a 5% risk" for an ASCVD event over the subsequent 10 years.


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ACC-AHA cardiovascular prevention guidelines drop cholesterol treatment goals