C-Reactive Protein: Not Ready for Population-Wide CVD Risk Assessment

Traditional risk factors alone are still the best predictors of CVD risk.

In two new studies, researchers have evaluated the predictive value of novel cardiovascular disease (CVD) risk markers, including C-reactive protein (CRP).

In one study, coauthored by a coinventor of a CRP assay, 15,048 women (age, 45) were followed for a mean of 10 years; 390 developed CVD. When CRP values were added to prediction models that included traditional risk factors (age, blood pressure, smoking status, and HDL and total cholesterol levels), prediction of which women would develop CVD was not improved. The researchers also examined how often women classified by traditional risk factors as having <5%, 5%–<10%, 10%–<20%, or 20% risk were recategorized when CRP results were incorporated: 12%–14% of women in each group were reclassified into the next lower category, and 2%–10% were transferred to the next higher category. The authors concluded that use of CRP assays could help direct preventive interventions. In another prospective U.S. cohort study, researchers assessed whether adding measurements of CRP or any of 18 other novel risk factors to traditional risk factors (age, race, sex, HDL and total cholesterol levels, systolic BP, use of antihypertensive agents, and smoking and diabetes status) improved prediction of incident coronary heart disease among nearly 16,000 adults (age, 45). Only lipoprotein-associated phospholipase A₂ showed a statistically significant increase in predictive value compared with traditional risk factors only; however, this increase was not clinically important.

The debate about the incremental value of measuring CRP and other novel markers will not end with these studies. Authors of a review that accompanies the Annals of Internal Medicine study determined that measuring CRP might add modest predictive ability for people at intermediate risk. But editorialists note that CRP might not be related causally to CVD and lowering CRP levels might not improve outcomes. Given that only one in three people with elevated BP or cholesterol levels achieves adequate control, we agree with Archives of Internal Medicine editorialists who recommend focusing on treatment and control of traditional risk factors. For now, routine screening of CRP levels appears unwarranted.

Reference:

Cook NR et al. The effect of including C-reactive protein in cardiovascular risk prediction models for women. Ann Intern Med 2006 Jul 4; 145:21-9.