Who Should Be Tested for C-Reactive Protein?

A number of studies over recent years have confirmed that C-reactive protein (CRP) is an inflammatory risk factor for heart disease, and new high-sensitivity (hsCRP) assays are now able to measure CRP at lower levels than previously possible, but confusion exists over whom to test.

A serum CRP level above 5 mg/l is associated with an almost three-fold increased risk of congestive heart failure. Patients with a first myocardial infarction have shown an adjusted 1.3-fold increased risk. Among the elderly, elevated plasma of hsCRP levels significantly predicts the risk of a future first ischemic stroke, and in others, a low-grade, chronic hsCRP measurement above 2.91 mg/l predicts a nearly three-fold higher risk of developing type 2 diabetes.

This does not mean that everybody should be tested, according to the US Centers for Disease Control and Prevention (Atlanta, GA, USA), which has provided the following recommendations regarding hsCRP testing. The entire adult population should not be screened for hsCPR for the purpose of cardiovascular assessment. However, measurement of hsCRP in those judged to be at intermediate risk may help an evaluation and indicate a need for therapy. In patients with acute coronary syndromes or stable coronary disease, hsCRP measurements may be useful for prognosis.

The CDC also recommends that measurement of hsCRP should be done twice, optimally two weeks apart, and the results averaged. When the level is above 10 mg/l, the test should be repeated and the relative risk category and average hsCRP levels be established as follows: low < 1 mg/l; average 1.0-3.0 mg/l; and high > 3.0 mg/l. The guidelines were presented during a report on CRP at the annual meeting of the American Association of Clinical Chemistry in Philadelphia (PA, USA).