What is Calprotectin - Stool ?

Also Known As: Fecal Calprotectin, Stool Calprotectin

Calprotectin is a protein released by a type of white blood cell called a neutrophil. When there is inflammation in the gastrointestinal (GI) tract, neutrophils move to the area and release calprotectin, resulting in an increased level in the stool. This test measures the level of calprotectin in stool as a way to detect inflammation in the intestines.

Intestinal inflammation is associated with inflammatory bowel disease (IBD) and with some bacterial GI infections, but it is not associated with many other disorders that affect bowel function and cause similar symptoms. Calprotectin can be used to help distinguish between inflammatory and non-inflammatory conditions.

IBD is a group of chronic disorders characterized by inflamed and damaged tissues in the lining of the intestinal tract. The cause of IBD is not known, but these diseases are thought to be due to an autoimmune process that has been triggered by a genetic predisposition, a viral illness, and/or an environmental factor. The most common inflammatory bowel diseases are Crohn disease (CD) and ulcerative colitis (UC).

People with IBD typically have flare-ups of active disease that alternate with periods of remission. During a flare-up, a person may experience frequent bouts of watery and/or bloody diarrhea, abdominal pain, weight loss, and fever. Between these flare-ups, symptoms frequently subside. Many people may go through extended periods of remission between flare-ups. Calprotectin testing can be useful in monitoring disease activity. The test is not specific or diagnostic for IBD, but it may be done to detect and evaluate the degree of inflammation.

How is it used?

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.