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New cholesterol calculator flawed, Harvard MDs say

NEW YORK — Last week, the nation’s leading heart organizations released a sweeping new set of guidelines for lowering cholesterol, along with an online calculator meant to help doctors assess risks and treatment options. But in a major embarrassment to the health groups, the calculator appears to greatly overestimate risk, so much so that it could mistakenly suggest that millions more people are candidates for statin drugs.

The apparent problem prompted one leading cardiologist, a past president of the American College of Cardiology, to call on Sunday for a halt to implementation of the guidelines.

“It’s stunning,” said the cardiologist, Dr. Steven Nissen, chief of cardiovascular medicine at the Cleveland Clinic. “We need a pause to further evaluate this approach before it is implemented on a widespread basis.”


The controversy set off turmoil at the annual meeting of the American Heart Association, which started this weekend in Dallas. Saturday night, the two organizations that published the guidelines — the American Heart Association and the American College of Cardiology — said that while the calculator was not perfect, it was a major step forward, and that patients and doctors should discuss treatment options rather than blindly following a calculator.

Dr. Sidney Smith, executive chairman of the guideline committee, said the associations would examine flaws in the calculator and determine if changes were needed. “We need to see if the concerns raised are substantive,” he said.

The problems were identified by two Harvard Medical School professors whose findings will be published Tuesday in The Lancet medical journal. The professors, Dr. Paul M. Ridker and Dr. Nancy Cook, had pointed out the problems a year earlier when the National Institutes of Health’s National Heart, Lung, and Blood Institute, which originally was developing the guidelines, sent a draft to each professor. Both reported back that the calculator was not working among the populations it was tested on by the guideline makers.


That was unfortunate because the committee thought the researchers had been given the professors’ responses, said Dr. Donald Lloyd-Jones, co-chairman of the guidelines task force and chairman of preventative medicine at Northwestern University.

Ridker and Cook saw the final guidelines and risk calculator Tuesday at 4 p.m., when a news embargo was lifted, and saw the problems remained.

On Saturday night, members of the association and the college of cardiology held a hastily called closed-door meeting with Ridker, who directs the center for cardiovascular disease prevention at Brigham and Women’s Hospital in Boston. He showed them his data and pointed out the problem.

On Sunday, officials from the organizations struggled with how to respond.

Other experts said there has not been a real appreciation of the difficulties with this and other risk calculators.

“I don’t think people have a good idea of what needs to be done,” said Dr. Michael Blaha, of Johns Hopkins University, who was not associated with forming the new guidelines.

Blaha said the problem might have stemmed from the fact the calculator uses as reference points the results from studies conducted more than a decade ago, when more people smoked and had strokes and heart attacks earlier in life.

For example, the guideline makers used data from studies in the 1990s to determine how various risk factors like cholesterol levels and blood pressure led to heart attacks and strokes over a decade of observation.


But people have changed, Blaha said. Among other things, there is no longer such a big gap between women’s risks and those of men at a given age. And people get heart attacks and strokes at older ages.

Ridker and Cook evaluated the risk calculator using three studies that involved thousands of people and continued for at least a decade. They knew the subjects’ characteristics at the start — their ages, whether they smoked, their cholesterol levels, their blood pressures. Then they asked how many had heart attacks or strokes in the next 10 years and how many would the risk calculator predict.

The answer was the calculator over-predicted risk by 75 to 150 percent, depending on the population.

A man whose risk was 4 percent, for example, might show up as having an 8 percent risk. With a 4 percent risk, he would not warrant treatment — the guidelines say treatment is advised for those with at least a 7.5 percent risk and that treatment can be considered for those whose risk is 5 percent.

“Miscalibration to this extent should be reconciled and addressed before these new prediction models are widely implemented,” Ridker and Cook wrote in The Lancet.

“If real, such systematic overestimation of risk will lead to considerable over-prescription.”

On Sunday, Smith said the concerns “merit attention.” But, he continued, “a lot of people put a lot of thought into how can we identify people who can benefit from therapy.” Further, said Smith, a professor of medicine at the University of North Carolina, “What we have come forward with represents the best efforts of people who have been working for five years.”


What are patients and doctors to do? On Sunday, there seemed to be no firm answers, except that those at the highest risk, like people who have had a heart attack or have diabetes, should take statins.

The guideline developers said they were not totally surprised by the problems.

“We recognize a potential for overestimates, especially at the high end of risk,” said Dr. David Goff, dean of the University of Colorado School of Public Health and cochairman of the guidelines’ risk assessment working group.

Not long after receiving the assessments from Ridker and Cook, the National Heart, Lung and Blood Institute removed itself from developing guidelines, saying that was not its mission. It handed responsibility to the heart association and American College of Cardiology.

Michael Lauer, director of the division of cardiovascular sciences at the institute, said on Sunday that it had received many reviews and sent them to the other groups, together with the responses of the guidelines’ authors.

“We left it to them to take it through their vetting process,” Lauer said.

And the groups did make changes in response to Ridker’s and Cook’s comments, Lloyd-Jones said.