Calprotectin: A marker for inflammatory bowel disease (IBD)
When unexplained and persistent stomach pains occur, one of the first reflexes is to suspect irritable bowel syndrome (IBS). IBS is actually the most common bowel disorder, affecting 10%-20% of the population. However, there are many other diseases, especially inflammatory conditions, related to the intestines.
How are they identified? During a stool analysis, calprotectin is a very effective marker that can help rule out the possibility of IBS. Other symptoms can also help rule out IBS.
Inflammation: The distinguishing factor
IBS is different from chronic inflammatory bowel disease by the absence of inflammation in the digestive tract.
Inflammation is a normal defence mechanism of the body against all kinds of attacks: foreign bodies (e.g., viral, bacterial or parasitic infections), injuries or burns. In the case of so-called autoimmune diseases, the defence system becomes disrupted and attacks normal body constituents. Crohn’s disease and ulcerative colitis are most likely caused by an inappropriate immune response to the bacteria normally present in the digestive tract.
The inflammatory response involves the mobilization of white blood cells around a site under attack. This phenomenon is sometimes even visible to the naked eye in the form of pus around a foreign body, such as a splinter. The whitish liquid contains, among other things, a very large number of white blood cells, also called neutrophils.
In the case of an inflammatory reaction in the digestive tract, neutrophils invade the affected portion of the intestinal mucosa. These white blood cells, and the damage they cause, can be seen on a biopsy of the intestinal wall, which is usually obtained during a colonoscopy.
Once neutrophils are present at an inflammation site, they release a range of specific markers, including a protein called calprotectin. These markers can also be found in the blood, where they indicate the presence of an inflammatory process, but do not reveal the affected organ.
A test that facilitates diagnosis
For inflammatory bowel disease, calprotectin can be detected directly in a stool sample. The presence of large amounts of calprotectin in the stool is a sure sign that neutrophils (indicating inflammation) are present in the intestinal lining.
In such cases, the doctor will prescribe additional tests (e.g., colonoscopy) to determine the cause and nature of the inflammation (and to rule out IBS). If calprotectin is not present (i.e., no inflammation) and other criteria are taken into account, irritable bowel syndrome may be considered and the patient’s medical care adjusted accordingly.