Biomarkers of Inflammation

Inflammation is an important part of normal responses to infection and injury. However, chronic activation of the immune system, due to aberrant responses to normal stimuli, can lead to the establishment of a persistent inflammatory state, which is a component of many disorders that are discussed according to the system involved. Major disorders with inflammation involve cardiovascular and nervous systems. Diseases such as diabetes and rheumatoid arthritis have are characterized by inflammation. The complement system is activated in virtually all inflammatory diseases and should therefore serve as a fertile source of biomarkers of inflammation. Traditionally, complement activation has been monitored by measurement of serum C3 and C4, the parent molecules and substrates for enzymatic activation. However, these assays are known to have limited utility for monitoring the inflammatory process.

ESR and CRP as Biomarkers of Inflammation

Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are two biomarkers of inflammation that have been commonly used in medical practice. There is strong (but incomplete) correlation between ESR and CRP values. CRP is a direct and quantitative measure of the acute phase reaction, an indicator of inflammatory activity and tissue damage, which correlates closely with the changes in inflammatory activity due to its fast kinetics. The ESR is an indirect measure of the acute phase reaction and reacts much more slowly than CRP to changes of inflammatory activity. Both ESR and CRP are valuable in discriminating pathology from harmless, often self-limiting diseases. ESR may be useful in the following:

  • • Establishing a “sickness index” in elderly persons who have nonspecific changes in health status and moderate probability of underlying disease.
  • • Screening for infection and monitoring treatment response for infections in specific settings.
  • • Diagnosing and monitoring temporal arteritis, polymyalgia rheumatica, and possibly other rheumatic diseases.
  • • Monitoring patients with treated Hodgkin disease or prostate cancer.
  • • Assessing iron deficiency in anemia of chronic disease (when correlated with serum ferritin level).

CRP may be useful in the following situations:

  • • Differentiation between a bacterial and a viral infection.
  • • Differentiation between a bacterial infection and an exacerbation of diseases like systemic lupus erythematosus.
  • • Monitoring of the effect of treatment (with serial measurements)
  • • Early detection of postoperative complications or intercurrent infections.
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