Serum levels of C-reactive protein (CRP) are useful to identify the presence and severity of inflammation. Recent studies reporting that moderate elevations of CRP correlate with future cardiovascular events validate the use of this test to assess cardiovascular risk. To identify these moderate elevations, performance of high-sensitivity assays for CRP (HSCRP) is recommended to better identify CRP variations. Kushner and Sehgal evaluated the recommendation for the use of HSCRP for cardiovascular risk assessment in the U.S. Preventive Services Task Force guidelines for clinical preventive services.
Before a screening test can be considered useful it must (1) accurately identify a condition in an asymptomatic person; (2) have reliable results; and (3) identify a condition early enough to allow beneficial intervention. Accuracy can be determined by the positive predictive value of a test. The current level of information available about CRP levels and cardiovascular disease is inadequate to determine actual risk or the rate of false-positive results. With these information deficiencies, accuracy and cost-effectiveness cannot be determined.
Reliability requires stability of results when they are repeated. The CRP can vary widely within one day in healthy persons, and genetic factors can affect CRP levels. Minor noninflammatory events can cause further test result variations in a single person. Finally, it is unclear how to intervene in persons with elevations of CRP in a way that would decrease future cardiovascular events. Reducing the CRP through treatment has not been demonstrated to reduce cardiovascular risk. The authors conclude that the usefulness of HSCRP screening to assess patients for future cardiovascular risk has not been demonstrated.