Coming of Age of C-Reactive Protein

Abstract

In a recently published prospective study comprising 28 000 women, Ridker et al 1 showed that C-reactive protein (CRP) is a better predictor of the risk of cardiovascular events than low-density lipoprotein (LDL) cholesterol. The implication of this and many other supporting studies is profound and will change the way we screen and manage our patients with atherosclerosis and its associated clinical syndromes. CRP is one of the acute phase proteins that increase during systemic inflammation. 2,3 Individuals without inflammation usually have CRP levels below 1 μg/mL; however, patients with bacterial infections, autoimmune diseases, and cancer frequently have CRP level as high as 100 μg/mL or even higher. It is clear that a high CRP level has no specificity in differentiating disease entities from one another. Despite its lack of specificity, CRP has now emerged as one of the most powerful predictors of cardiovascular risk. Even more remarkable, CRP’s predictive power resides in the range between 1 to 5 μg/mL, which was previously regarded to be normal in the era preceding the high-sensitivity CRP test. In fact, tests showing serum CRP levels greater than 10 μg/mL in apparently healthy men or women should be repeated to exclude occult infection or other systemic inflammatory process (see Figure). To understand CRP’s transition from an acute phase protein to a most useful inflammatory biomarker for predicting future cardiovascular events, we must know more about the role of the immune system in the pathogenesis of atherosclerosis.