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DALLAS -- The dust-up over the new cardiovascular disease prevention guidelines -- already named "Calculator-gate" -- prompted the American Heart Association and American College of Cardiology to stage a public defense at a hastily assembled press briefing here.
Although there are four guidelines in the new prevention package it is the assessment of risk -- the so-called risk calculator -- and the recommendation that statins be used as primary prevention that have drawn fire.
The issue took on increased intensity when word reached AHA and ACC leaders that , and , of Brigham and Women's Hospital in Boston, had data showing that the new risk calculator greatly overestimates the risk of myocardial infarction and stroke by 75% to 150%, potentially resulting in the initiation of statin therapy in patients who don't need it.
Guidelines writers and leaders from the two organizations met with Ridker -- who was not invited to the press briefing -- Saturday night to parse the data, which were due to be published in a commentary in The Lancet and were featured in a story in , an article that prompted a media free-for-all epitomized by CNN reporter Elizabeth Cohen, who monitored the press briefing by phone.
Cohen sought to indict the new risk calculator by noting she was using it to track the risk of middle-age man with normal LDL and normal BMI "I put his numbers into your calculator and it tells me he should be on a statin."
The AHA panelists pointed out that she was actually using an old risk calculator from 2002.
Overestimation of Risk
Although Ridker and Cook were generally supportive of the new guidelines in their commentary -- calling them a "a major step in the right direction" -- they questioned the accuracy of the risk equations used to stratify patients. They applied the algorithms for the prediction of 10-year risk of MI and stroke to three large-scale, primary prevention cohorts -- the Women's Health Study, the Physicians Health Study, and the Women's Health Initiative Observational Study -- and found systematic overestimation of risk.
They also pointed to the guidelines themselves, which describe overestimation of risk in two of the validation cohorts in which the new equations were tested -- MESA and REGARDS.
"Thus, based on data from these five external validation cohorts, it is possible that as many as 40% to 50% of the 33 million middle-aged Americans targeted by the new ACC/AHA guidelines for statin therapy do not actually have risk thresholds exceeding the 7.5% level suggested for treatment," Ridker and Cook wrote. "Miscalibration to this extent should be reconciled and addressed in additional external validation cohorts before these new prediction models are widely implemented."
That overestimation of risk was noted more than a year ago, according to , dean of the Colorado School of Public Health and co-chair of the writing group for the risk assessment guideline. But even so, the new risk equation performed comparably with the older Adult Treatment Panel III risk calculator.
, chair of the department of preventive medicine at Northwestern University's Feinberg School of Medicine in Chicago and co-chair of the risk assessment guideline, noted that -- though the overestimation was seen across the range of risk -- the effect was greatest among those with the highest predicted risk.
The explanation, he said, is that the highest-risk patients in the cohorts studied were identified and started on statins, resulting in lower-than-expected event rates.
As for the data from Ridker and Cook, Lloyd-Jones said that the cohorts they examined were not representative of the overall U.S. population and included participants with low levels of risk, in whom the risk calculator would be expected to overestimate risk.
Too Many People on Statins?
Goff said that under the new guidelines roughly 30 million Americans ages 40 to 75 -- about one-third -- would be recommended for potential statin therapy for primary prevention.
To put that number in context, he pointed out that about 70 million people in the U.S. meet criteria for guideline-recommended treatment of high blood pressure.
Considering that fact and the fact that treatment of cardiovascular disease represents such an enormous burden on society, the 30 million patients potentially eligible for statin therapy "sounds about right to me," Goff said, "and I think it's the appropriate thing to do."
The guideline authors bristled at the suggestion that simply passing the 7.5% risk threshold advocated in the guidelines for consideration of starting statin therapy would automatically result in a prescription, pointing out that the guidelines themselves stress the importance of using the risk information to spark a conversation between the patient and the physician about the appropriate course of action, which may or may not include a statin depending on the patient's specific situation.
The calculator "is the start of the risk discussion, it's not the end," said , of Northwestern Medicine and chair of the panel that wrote the cholesterol guideline. "We've put the patient, we've put the physician back into crucial decision making."
Stone noted that the guideline committee tried to align the recommendations with best available scientific evidence, noting that if that is not the basis for guidelines "then you are going to have guidelines based on the loudest people in the room. That can't be right."
Call for Delayed Implementation of the Guidelines
The issues raised by Ridker and Cook, led to call for a delay in the implementation of the guidelines, but the AHA/ACC said that was not going to happen.
"We intend to move forward with the implementation of these guidelines," said , a professor of medicine at the University of North Carolina at Chapel Hill and chair of the executive committee for the new set of guidelines.
Speaking for the AHA and ACC, said, "we think we've done our due diligence. We have faith and trust in our investigators.
"Right now, we are very confident this is the very best available evidence to make recommendations so that practitioners can take care of their patients," she added.
The current guidelines "should not be put 'on hold'" according to , head of the section of preventive cardiology at the University of Alabama at Birmingham. "The guidelines are based on the current clinical trial evidence."
"And the guidelines are very clear that there should be discussion of expected benefit and risk between physician and patient before treatment is instituted or withheld," she continued in an email to ѻý. 'The controversy around the risk calculator for individuals without high risk based on existing disease obviously needs to be resolved, and there may need to be some re-calibration of the current equations if they overestimate risk in contemporary populations."
"As we've always done with our guidelines," said Smith, a past president of the AHA, "if we think there's something that can make them better, you can count on us to do it."
All of the panelists at the press briefing said that the risk calculator and the guidelines would be updated as new information became available.
UPDATE: This article, originally published Nov. 18, 2013, at 3:50 p.m., was updated with new material (Nov. 18, 2013, at 6:50 p.m.).