C-Reactive Protein and Erythrocyte Sedimentation Rate in Orthopaedics

C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) are known as acute phase proteins, which reflect a measure of the acute-phase response. The term “acute phase” refers to local and systemic events that accompany inflammation. Local responses include vasodilation, platelet aggregation, neutrophil chemotaxis, and release of lysosomal enzymes. Systemic responses include fever, leukocytosis, and a change in the hepatic synthesis of acute phase proteins (a hepatic protein, which by definition, increases or decreases in serum concentration by at least 25%). Stimuli to the acute phase include many different forms of tissue injury, such as infection, immuno/allergic reaction, thermal injury, hypoxic injury, trauma, surgery, and malignancy. The clinical use of acute phase proteins is as an aid to diagnosis [15]. Because the acute phase response is relatively non-specific, the value of measuring acute-phase protein concentrations is to assess the extent of inflammation reflecting momentary disease activity. Similar to tumor markers, acute-phase proteins may monitor the course of disease in response to therapeutic intervention. CRP and ESR are not the only acute phase proteins. Other acute-phase proteins include transport proteins (haptoglobin, ceruloplasmin, 1-trypsin inhibitor, etc.), coagulation proteins (fibrinogen, prothrombin, etc.), and complement components (C3, C4, C5, etc.). What makes CRP and ESR markers of choice in monitoring the acute phase is that they increase in concentration relatively high compared to basal concentration, have a relatively short lag time from the moment of stimulus, and are cost-effective [15].