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Experts question risk calculator released with new cholesterol guidelines

Newly-released cholesterol treatment guidelines that may put more Americans on statin drugs might be flawed by bad math, some experts warn.

Top cardiology groups are releasing new guide... 01:19
The new guidelines were released last week by the American Heart Association and American College of Cardiology. They called for prescribing moderate to high dose statins for four groups of Americans that studies suggest have the greatest odds of preventing heart attacks and strokes while taking the drugs: People who have heart disease, people with an LDL, or "bad" cholesterol level of 190 mg/dL or higher, people with Type 2 diabetes who are between 40 and 75 years old and individuals with an estimated 10-year risk of heart disease of 7.5 percent or higher who are between 40 and 75 years of age.

That last risk factor is determined through a calculation, which experts are now saying does not add up, the New York Times first reported.

The National Institutes of Health's National Heart, Lung, and Blood Institute sent the guidelines out in draft form last year. The calculator factored in some patients' blood test results and other factors that could influence heart disease risk, such as ethnicity.

However, cardiologist Dr. Paul M. Ridker and epidemiologist Dr. Nancy Cook, both of Harvard Medical School, told the Times they found the potential calculator at that time overestimated heart disease risk. The researchers had tested the calculations among different patient populations.

They reported that the calculator wasn't working, but the committee may never have received those responses, according to the Times. The researchers noticed the problems remained last Tuesday when the new guidelines were unveiled.

They found the calculator could overestimate heart disease risk by 75 to 150 percent, depending on the patient.

"Miscalibration to this extent should be reconciled and addressed before these new prediction models are widely implemented," Ridker and Cook wrote in the Nov. 18 issue of The Lancet, according to the paper. "If real, such systematic overestimation of risk will lead to considerable overprescription."

For example, the CBS Evening News reported last week that a 50-year-old white male with treated high blood pressure, a total cholesterol of 220, and an HDL reading of 45 was found to have a 5 percent risk for heart disease in 10 years, according to the calculator. For black Americans, those same numbers work out to an 8.9 percent 10-year risk, and statin treatment may be warranted, per the new guidelines.

Dr. Neil J. Stone, chair of the expert panel that wrote the new guidelines and a professor of medicine at Northwestern University Feinberg School of Medicine in Chicago, previously told the CBS Evening News that the calculator does not replace a conversation with a doctor.

"Everyone is different, we all have our risks and our individual factors that make treatment more beneficial or may make treatment more difficult. And to deal with that, we're urging a patient-clinician discussion," Stone said.

The Times' report adds that an emergency meeting was convened Saturday night at the AHA's 2013 annual meeting in Dallas to discuss the researchers' findings.

"If experts are having this debate over the new guideline, then what are practitioners and patients sitting on the sidelines going to think?" Dr. Peter Libby, chair of the department of cardiovascular medicine at Brigham and Women's Hospital in Boston, told the Boston Globe.

Dr. Donald Lloyd-Jones, chair of the department of preventive medicine at Northwestern University's Feinberg School of Medicine, told HealthDay he was at the AHA emergency meeting with Ridker. He said their calculations are skewed because they looked at studies involving people who are younger and healthier than typical Americans.

"These people exist in the U.S. population, but it's a very healthy, skewed group," he said. "I think all of us would like to see Dr. Ridker's data, and see that play out in scientific discussion rather than in the media," Lloyd-Jones said.

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