Clinical calculators over-estimate heart attack risk

26-02-2015

Most risk calculators used by clinicians to gauge a patient’s chances of suffering a heart attack and guide treatment decisions appear to significantly overestimate the likelihood of a heart attack.

This is according to a study by investigators at Johns Hopkins and other institutions, reported February 17 in Annals of Internal Medicine, which suggests that four out of five widely used clinical calculators considerably overrate risk.

This includes the most recent one unveiled in 2013 by the American Heart Association and the American College of Cardiology amid controversy about its predictive accuracy.

To check the accuracy of each one of five risk calculators, the investigators compared the number of predicted versus actual heart attacks and strokes among a group of more than 4,200 MESA participants, ages 50 to 74, followed over a decade. All people involved in the research were free of cardiovascular symptoms at the beginning of the study and had no history of heart attacks and strokes.

Four out of five risk scores analyzed in the study overestimated risk by anywhere from 37 percent to 154 percent in men and 8 percent to 67 percent in women.

The new American Heart Association calculator overestimated risk by 86 percent in men and by 67 percent in women. In the group with a predicted risk score between 7.5 to 10 percent — the threshold at which initiation of stain is recommended — the actual rate of heart attacks and strokes was only 3 percent in men and 5 percent in women, well below the risk level at which statins should be considered.

The research team said the results of the study underscore the perils of overreliance on standardized algorithms and highlight the importance of individualized risk assessment that includes additional variables, such as other medical conditions, family history of early heart disease, level of physical activity, and the presence and amount of calcium build-up in the heart’s vessels.

“Our results reveal a lack of predictive accuracy in risk calculators and highlight an urgent need to re-examine and fine-tune our existing risk assessment techniques,” said senior investigator Michael Blaha, director of clinical research at the Johns Hopkins Ciccarone Center for the Prevention of Heart Disease.

“The take-home message here is that as important as guidelines are, they are just a blueprint, a starting point for a conversation between patient and physician about the risks and benefits of different treatments or preventive strategies.”

In addition to patient safety, risk overestimation has important public health and economic ramifications.

“For example, cholesterol-lowering medicines, while clearly cost-effective in high-risk patients, are less so among low-risk patients,” said lead author Andrew DeFilippis, assistant professor of medicine at the University of Louisville and adjunct assistant professor of medicine at the Johns Hopkins Ciccarone Center for the Prevention of Heart Disease. “Therefore, overestimation of risk could lead to more health care spending, less health gain, and unnecessary exposure to drug side effects.” 

Risk Management, US, Johns Hopkins, MESA, Michael Blaha, Andrew DeFilippis