Inflammatory markers are serum proteins that are produced in response to inflammation. These proteins are mainly produced by the liver in response to stress and are called acute phase reactants. These inflammatory markers are not diagnostic of inflammation but reflect abnormalities seen in autoimmune diseases, infections, malignancies, and other illnesses.
Several tests for specific protein markers can be employed to assess acute or chronic inflammation; however, none of these tests are necessarily specific for a given autoimmune disease. One or more of the following markers may be elevated in acute or chronic inflammation:
- Ferritin
- Ceruloplasmin
- Haptoglobin
- Albumin
- Fibrinogen
Erythrocyte sedimentation rate (ESR)
ESR, the rate that red blood cells (RBC) settle in a tube, is typically elevated in inflammation. Multiple factors can influence the ESR, including the patient's age, gender, RBC morphology, hemoglobin concentration, and serum levels of immunoglobulin. While the ESR is not a diagnostic test, it can be used to monitor disease activity and treatment response and signal that inflammatory or infectious stress is present.
C-reactive protein (CRP)
CRP (including high-sensitivity CRP) was discovered and named for its reactivity to the C polysaccharide in the cell wall of S. pneumoniae. CRP helps in the process of phagocytosis and activates the complement system. CRP production is controlled by cytokines IL-1, IL-6, and TNF-alpha. Changes in serum CRP concentration occur faster than ESR. Therefore, CRP may be a better reflection of current inflammation. Unlike the ESR, CRP is a fairly stable serum protein whose measurement is not time-sensitive and is not affected by other serum components. In addition, the magnitude of inflammation directly relates to the concentration of CRP. More recently, high-sensitivity CRP has been utilized and may better quantify lower levels of inflammation.
