The efficiency of a method that is being widely used to predict risk of major heart problems has been questioned in a new study as it is likely to over or underestimate the risk for millions of Americans.
The method in question is the simplified version of the so-called Framingham model, which is used to estimate a patient's 10-year risk of a heart attack, stroke, or other coronary event based on risk factors such as age, cholesterol levels, blood pressure, and smoking.
National guidelines recommend using the risk estimates generated by the Framingham model to classify patients as among one of three risk groups.
Researchers at the San Francisco VA Medical Center and the University of California assessed data from 2,543 subjects who participated from 2001 to 2006 in National Health and Nutrition Examination Surveys sponsored by the Centers for Disease Control and Prevention.
For each subject, the researchers calculated risk based on the original Framingham model and on the simplified model, and compared the differences, "which turned out to be substantial for many patients," said Michael Steinman, senior author of the paper.
Under the point-based system, 15 percent of the subjects were classified as being at a different level of risk than they were under the original model.
Nationwide, said the authors, 5.7 million Americans would be placed into different risk groups using the point-based model than they would be using the original model, with 3.9 million misclassified into higher risk groups and 1.8 million misclassified into lower risk groups.
"Across the group, on average, these statistical differences balance out. But for individual patients, they are potentially important. A lot of individuals would be treated differently - either more aggressively or less aggressively - using the point-based model.
"While the point-based system is a substantial improvement over having no standardized method for predicting risk, just about any computer or PDA in use today can calculate the original Framingham model.
"This means that your doctor can calculate your risk just as easily using the complex equation, which is likely to be more accurate than the point-based system. So there's not much reason to use the point-based system anymore in most instances," said Steinman.
The study appeared in the Journal of General Internal Medicine.