National Cholesterol Education Program risk assessment and potential for risk misclassification.

Background: The National Cholesterol Education Program Adult Treatment Panel report from 2001 (ATP III) recommends clinicians calculate 10-year coronary risk using multivariable methods only for adults with 2 or more risk factors. We aimed to determine who would be falsely classified as low risk using this approach.
Methods: We studied 4097 adults aged 20 to 79 years without diagnosed cardiovascular disease or diabetes from the National Health and Nutrition Examination Survey from 1999 to 2002. We determined the proportion with fewer than 2 risk factors who nonetheless had estimated 10-year risk of cardiac death or myocardial infarction > or =10% using multivariable methods.
Results: Among persons with fewer than 2 risk factors, 5.3% (95% confidence interval 4.7 to 6.1%), had a 10-year risk > or =10% using the Framingham Risk Score and would be misclassified using the risk factor counting method (this corresponds to approximately 5,640,000 U.S. adults). Compared to individuals whose classification was unchanged, those misclassified as low risk were older (P<0.001) and more likely male (85.5% vs. 41.2%, P<0.001).
Conclusions: Relying on the ATP III risk factor counting method rather than determining risk using multivariable methods in all patients resulted in misclassifiying as low risk over 5 million adults with at least moderately high risk of coronary heart disease, most of whom are middle-aged and older men.