Measurement of faecal calprotectin is a biochemical test for intestinal inflammation, including inflammatory bowel disease. Under specific clinical scenario, the test may eliminate the need for invasive colonoscopy or radio-labelled white cell scanning.
Structure and function
Calprotectin is a 36kDa calcium and zinc binding protein expressed by the gene S100 calcium-binding protein A8, S100A8. It accounts for 30 to 40% of neutrophils' cytosol. In vitro studies show it has bacteriostatic and fungistatic properties. It is resistant to enzymatic degradation, and can be easily measured in faeces.
Use as a surrogate marker
|Reference ranges for calprotectin|
|Patient age||Upper limit||Unit|
|2–9 years||166||µg/g of faeces|
|≥ 60 years||112|
Inflammatory bowel diseases (IBD) are a group of conditions that cause a pathological inflammation of the bowel wall. Neutrophils influx into the bowel lumen as a result of the inflammatory process. Measurement of faecal calprotectin has been shown to be strongly correlated with 111-indium-labelled leucocytes - considered the gold standard measurement of intestinal inflammation. Levels of faecal calprotectin are normal in patients with irritable bowel syndrome (IBS).
Although a relatively new test, faecal calprotectin is regularly used as indicator for IBD during treatment and as diagnostic marker.
Specific indications for measuring calprotectin are in:
- Distinguishing inflammatory bowel disease (IBD) from functional bowel disease (IBS), and thus avoid the need for invasive tests such as colonoscopy.
- Assessing efficacy of IBD treatments.
- Predicting relapses or flares of IBD.
- Offer an alternate diagnostic test for patients phobic of needles or endoscopy.
Although faecal calprotectin correlates significantly with disease activity in people with confirmed IBD, faecal calprotectin can be false-positive in some conditions. Most importantly, intake of proton pump inhibitors (e.g. omeprazole) is associated with significantly elevated calprotectin values.
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