Revision 11 for 'Fecal calprotectin'

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Fecal calprotectin

Fecal calprotectin (FCAL) is a protein which is a marker of inflammation of the gut used as a diagnostic tool and marker of disease activity for Crohn disease and ulcerative colitis.

Biochemistry

Calprotectin is a protein complex from the S-100 family, which is formed of three polypeptide chains, two heavy and one light 2. It was first purified in 1980 and called L1 protein by the group that discovered it, although like many proteins has had multiple names 2.

Distribution

It is found in especially heavy concentrations in neutrophils and monocytes, and more generally within skin cells, with an organ distribution including the lungs, gastrointestinal tract, oral and cervical mucosae and associated body fluids/secretions.

During the inflammatory process it is secreted by neutrophils and macrophages in the gut and is assayable in the feces. 

Assay

There are many commercially-available testing kits for calprotectin, many using ELISA (enzyme-linked immunosorbent assay) techniques. 

Clinical

Fecal calprotectin is primarily employed in two scenarios:

  1. distinguish inflammatory bowel disease from irritable bowel syndrome
  2. assay disease activity in inflammatory bowel disease, including acute exacerbations and response to treatment

The use of fecal calprotectin as a screening tool for colorectal carcinoma has been explored however its specificity is too low to be useful in the general population 1.

No consensus exists on correlation between calprotectin levels and activity of bowel disease on cross-sectional imaging, as studies have come to different conclusions, a recent study, albeit a small cohort, showed a weak correlation at best 4.

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