Calprotectin is a marker of inflammation found extensively in the cytoplasm of neutrophils and it has been shown to be extremely useful as an aid for diagnosis of inflammatory bowel disease (IBD) such as Crohn’s disease, ulcerative colitis and indeterminate colitis. The fecal calprotectin test can distinguish IBD from irritable bowel syndrome (IBS), and can be used monitor the severity of IBD.
Calprotectin is formed as a heterodimer of S100A8 and S100A. Activation of the intestinal immune system leads to recruitment of cells from the innate immune system, including neutrophils which release calprotectin upon activation. As the inflammatory process progresses, the released calprotectin is absorbed by the fecal material before it is excreted from the body. The amount of calprotectin present in the feces is proportional to the number of neutrophils within the gastrointestinal mucosa. Large amounts of calprotectin indicate IBD, while low or normal levels suggest IBS.
Commercial diagnostic fecal assays for Calprotectin are quantitative ELISA or turbidimetric immunoassays that use monoclonal or polyclonal antibodies to human calprotectin. Turbidimetric formats are appropriate on most clinical chemistry analyzers.