CRP is used mainly as a marker of inflammation. Apart from liver failure, there are few known factors that interfere with CRP production. Interferon alpha inhibits CRP production from liver cells which may explain the relatively low levels of CRP found during viral infections compared to bacterial infections.
Measuring and charting CRP values can prove useful in determining disease progressor the effectiveness of treatments.
Normal concentration in healthy human serum is between 5 and 10 mg/L, increasing with aging. Higher levels are found in late pregnant women, mild inflammation and viral infections (10–40 mg/L), active inflammation, bacterial infection (40–200 mg/L), severe bacterial infections and burns (>200 mg/L).
CRP is a more sensitive and accurate reflection of the acute phase response than the ESR(Erythrocyte Sedimentation Rate). ESR may be normal while CRP is elevated. CRP returns to normal more quickly than ESR in response to therapy.