Usefulness of C-reactive protein test questioned

Feb 27 2007

Researchers with Dartmouth Medical School and the Veterans Affairs Outcomes Group at the White River Junction (Vt.) VA Medical Center are questioning the usefulness of the C-Reactive Protein (CRP) test for guiding decisions about the use of cholesterol-lowering medication.

The researchers show that adding CRP testing to routine assessments would increase the number of Americans eligible for cholesterol-lowering treatment by about 2 million if used judiciously, and by over 25 million if used broadly - with most of these people being at low risk for heart attacks or heart disease. The authors argue that the medical community should focus energies on treating high-risk patients before expanding the pool to include so many low-risk patients. Their study was published in the February issue of the Journal of General Internal Medicine.

"There is a push to use this test, and that probably doesn't make much sense," says Steven Woloshin, one of the authors on the paper and an associate professor of community and family medicine at Dartmouth Medical School (DMS).

According to co-author Lisa Schwartz, associate professor of medicine at DMS, "A general population use of the test would identify millions of low-risk people, and we don't know if exposing them to cholesterol medications will do more good than harm. Plus, focusing on low-risk people seems misplaced since over half of high-risk people, who we know are helped by treatment, remain untreated."

Woloshin and Schwartz's co-authors are H. Gilbert Welch and Kevin Kerin, all of whom are affiliated with Veterans Affairs Outcomes Group and Dartmouth Medical School. Woloshin, Schwartz, and Welch are also part of Dartmouth's Center for Evaluative Clinical Sciences.

For this study, the team analyzed nationally representative data from more than 2,500 people who participated in the 1999-2002 National Health and Nutrition Examination Study (NHANES). They discovered that adding a broadly applied CRP strategy to current cholesterol-based guidelines would make over half the adults age 35 and older in the United States eligible for lipid-lowering therapy.

"Before expanding treatment criteria to include more low-risk patients' for whom treatment benefit is not established - we should ensure the treatment of high-risk patients where the benefit of therapy is clear," says Woloshin.

The authors note that their study has several limitations. Since the NHANES data did not include some cardiovascular risk factors (e.g., presence of an aortic abdominal aneurysm or peripheral artery disease), the number of people in the highest risk groups may be underestimated. Second, not every patient made eligible for cholesterol-lowering therapy by the CRP test will get treated; some will try lifestyle measures first (although data from other studies suggest these measures will only succeed for a minority).