C-reactive protein (CRP) is the classic acute phase protein to inflammatory reactions. It is synthesized by the liver and consists of five identical polypeptide chains that form a five-membered ring having a molecular weight of 120000 daltons. CRP is the most sensitive of the acute phase reactants and it’s concentration increases rapidly during inflammatory processes. Complexed CRP activates the complement system beginning with C1q. C-reactive protein promotes phagocytosis of many bacteria in the presence of calcium ions. It activates the classic complement pathway in the absence of specific antibody to opsonize bacteria such as E. coli and S. pneumonii. C-reactive protein may be an important early defense mechanism in certain infections. It is one of the most consistently elevated and fastest reacting acute phase reactants and is therefore a useful marker for disorders of inflammation or tissue necrosis.
Recent studies have shown that monitoring C-reactive protein was almost twice as good as cholesterol screening in predicting a person’s risk of a heart attack or peripheral vascular disease. The reason is that inflammation is often the culprit in blocked arteries, not cholesterol. During an event, serum levels of C-reactive protein may elevate from normal (5-20 mg/L) to over 500 mg/L. Sensitive CRP measurements have been used and discussed for early detection of infection in pediatrics and risk assessment of coronary heart disease.
Various assay methods are available for CRP determination, such as nephelometry and turbidimetry, as well as, latex particle enhaced immunological agglutination.