Measurement of faecal calprotectin is a biochemical test for inflammatory bowel disease. It replaces the need for invasive colonoscopy or radio-labelled white cell scanning in many clinical scenarios.
Calprotectin is a 36kDa calcium and zinc binding protein expressed by the gene S100 calcium-binding protein A8, S100A8. It accounts for 60% 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.[1]
| Reference ranges for calprotectin | ||
|---|---|---|
| Patient age | Upper limit | Unit |
| 2-9 years | 166[2] | µg/g of feces |
| 10-59 years | 51[2] | |
| ≥ 60 years | 112[2] | |
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.[3]
The main diseases that cause an increased excretion of faecal calprotectin are Crohn's disease, ulcerative colitis and neoplasms (cancer). Levels of faecal calprotectin are normal in patients with irritable bowel syndrome (IBS).[4]
Still a relatively new test, faecal calprotectin is not in widespread use.
Specific indications for measuring calprotectin are in:[5]