C-Reactive protein

Keywords: CRP

Specimen:

5 mL blood in plain tube.

Method:

Immunoassay.

Reference Interval:

< 5 mg/L.

For high sensitivity assays (hs-CRP):

Low risk: < 1.0 mg/L

Average risk: 1.0-3.0 mg/L

Application:

Assessment of acute phase reaction in inflammatory, infective and neoplastic disorders;

monitoring disease activity, particularly in inflammatory arthritis;

monitoring patients after premature rupture of the membranes, for developing infection; and

assessment of risk factors for Myocardial infarction (hs-CRP). 

Marginally raised hs-CRP, and values within the normal range, have been demonstrated to be an independent risk factor for coronary artery disease. However, the applicability of measuring serum CRP for screening in asymptomatic populations for coronary artery disease risk remains unclear.

Interpretation:

Elevation indicates acute phase response or active disease in chronic inflammatory disorders.

CRP is a more sensitive early indicator of an acute phase response than the ESR. It also returns towards normal more rapidly with improvement or resolution of the disease process. The test is less sensitive than the ESR for some disorders eg, ulcerative colitis, SLE.

In patients at risk for Myocardial infarction, and without other causes of an acute phase response, the presence of slightly elevated or even high normal hs-CRP indicates a greater risk of myocardial infarction. The use of high sensitivity CRP in clinical practice remains undecided.

See also Erythrocyte sedimentation rate and Acute phase reactants.

Reference:

Young B et al. Pathology 1991; 23: 118-124.

Jialal I and Devaraj S. Am J Clin Pathol 2001; 116: 108-115.