0217-News-Calculating Risk_BlogSeveral risk assessment tools, including one from the American Heart Association and American College of Cardiology, were found to overestimate heart attack and stroke risk, according to a study published Monday in the Annals of Internal Medicine.

But experts who developed the AHA/ACC risk calculator said they already knew about the risk overestimation before releasing the assessment tool and guidelines in 2013.

“The overall findings are not news at all,” said Donald Lloyd-Jones, M.D., chair of the department of preventive medicine at the Northwestern Feinberg School of Medicine and an AHA volunteer who helped write the risk assessment guidelines. “We actually did much of this exercise ourselves in the guideline document.”

Because the AHA/ACC equation was developed using data from whites and African-Americans, Lloyd-Jones said the guideline authors cautioned that the calculator would overestimate risk for Chinese-Americans and Hispanic-Americans, who made up a third of patients in the new study.

“A more appropriate analysis would have looked at each ethnic group separately in order to provide insight on this important issue,” Lloyd-Jones said.

Among 4,200 older Americans taking part in the Multi-Ethnic Study of Atherosclerosis, or MESA, four out of five risk calculators analyzed in the study overestimated risk by 37 percent to 154 percent in men and 8 percent to 67 percent in women over a 10-year period. The AHA/ACC calculator overestimated risk by 86 percent in men and by 67 percent in women.

Although participants had no history of heart attack or stroke, about 80 percent were being treated with a cholesterol-lowering statin or other preventive therapy during the study. The AHA/ACC risk equation, however, was developed to predict the cardiovascular events that would occur over 10 years if people were never treated, Lloyd-Jones said.

“This high level of treatment renders this cohort inappropriate for evaluating how the equations work in an untreated natural history cohort, the target of the equations,” he said. These patients may instead be better suited for studies that seek to understand lingering risk in a highly treated population, Lloyd-Jones said.

The AHA/ACC risk calculator is recommended for 40- to 79-year-olds every four to six years. It measures a person’s risk for a heart attack or stroke within the next 10 years based on race, gender, age, total cholesterol, HDL (good) cholesterol, blood pressure, use of blood pressure medication, diabetes status and smoking status.

People with a 7.5 percent or higher risk should talk with their healthcare provider about ways to reduce their risk, including lifestyle changes such as a healthier diet and more exercise and whether a statin drug may be appropriate, according to separate cholesterol guidelines released by the AHA and ACC in 2013.

David Goff, M.D., Ph.D., was among the experts who wrote the AHA/ACC risk assessment guidelines and said that although he does not want to squelch debate over the AHA/ACC risk assessment tool, the focus should be on how to best prevent heart disease and stroke.

“The people writing these papers share the same goal we do — a world free of cardiovascular diseases and stroke,” said Goff, dean of the Colorado School of Public Health. “We’re trying to figure out the best way to get there. And while we’re figuring it out, we have to implement policy along the way.

“We recognize that we don’t know everything now, but we know enough to do better than we have been doing,” Goff added.

The AHA/ACC guidelines on risk assessment and cholesterol both advise doctors to consider a patient’s overall health in decisions about preventive treatment.

Preventive cardiologist Lloyd-Jones said that estimating the likelihood that one of his patients will have a heart attack or stroke within the next decade is just the first step.

“From there you start to figure out, how much can I reduce that risk if they stop smoking, if they take a statin or an aspirin,” he said. “It will never be a precise number, but without some way of quantifying, we’re very poor at eyeballing risk.”

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