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.
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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- Fecal calprotectin as a correlative marker in clinical severity of infectious diarrhea and usefulness in evaluating bacterial or viral pathogens in children. J Pediatr Gastroenterol Nutr. 2012 Nov;55(5):541-7.
- Role of faecal calprotectin as non-invasive marker of intestinal inflammation. Costa F et al. Dig Liver Dis. 2003 Sep;35(9):642-7
- Calprotectin is a stronger predictive marker of relapse in ulcerative colitis than in Crohn's disease. Costa F et al. Gut. 2005 Mar;54(3):364-8.
- A simple method for assessing intestinal inflammation in Crohn's disease Tibble et al. Gut.2000; 47: 506-513
- D'Haens G, Ferrante M, Vermeire S, Baert F, Noman M, Moortgat L, Geens P, Iwens D, Aerden I, Van Assche G, Van Olmen G, Rutgeerts P. Faecal calprotectin is a surrogate marker for endoscopic lesions in inflammatory bowel disease. Inflamm Bowel Dis. 2012 Dec;18(12):2218-24. doi: 10.1002/ibd.22917. Epub 2012 Feb 16.
- Poullis, Andrewa; Foster, R.a; Mendall, Michael A.b. Proton pump inhibitors are associated with elevation of faecal calprotectin and may affect specificity. European Journal of Gastroenterology & Hepatology: May 2003 - Volume 15 - Issue 5 - p 573‐574. http://journals.lww.com/eurojgh/Citation/2003/05000/Proton_pump_inhibitors_are_associated_with.21.aspx