Calprotectin is a stool (fecal) test that is used to detect inflammation in the intestines. Intestinal inflammation is associated with, for example, some bacterial infections and, in people with inflammatory bowel disease (IBD), it is associated with disease activity and severity. The calprotectin test is not diagnostic but may be used to distinguish between IBD and non-inflammatory disorders and to monitor the severity of IBD.
A healthcare practitioner may order a calprotectin test to help investigate the cause of a person’s persistent watery or bloody diarrhea. The test may be ordered along with other stool tests, such as a stool culture to detect a bacterial infection, a test for ova and parasites (O&P), a stool white blood cell test, and/or a fecal occult blood test (FOBT). If a healthcare practitioner suspects inflammation, then a blood test that detects inflammation in the body, such as a C-reactive protein (CRP), or an erythrocyte sedimentation rate (ESR) if CRP is not available, may also be ordered. Testing is performed both to help determine what is causing a person’s symptoms and to rule out conditions with similar symptoms. This means that additional blood and stool testing may be performed depending on the suspected causes.
A calprotectin test may be ordered to help determine whether an endoscopy is indicated if IBD is suspected. A diagnosis of IBD is usually confirmed by performing an endoscopy (colonoscopy or sigmoidoscopy) to examine the intestines and by obtaining a small tissue sample (biopsy) to evaluate for inflammation and changes in tissue structures. This testing is invasive and is less likely to be necessary if inflammation is not present.
A calprotectin test may be ordered if a person with IBD has symptoms that suggest a flare-up, both to detect disease activity and to help evaluate its severity. For example, if a person has a moderately elevated calprotectin, then testing may be repeated several weeks later to see if it has stayed moderately elevated, increased, or returned to normal.