Stool testing involves providing a small quantity of stool to be examined in the laboratory. This type of test can provide useful information regarding the presence/severity of inflammation by examining faecal calprotectin (FC) levels.
The FC test is a measurement of the protein calprotectin present in stool. This protein is released at the area of inflammation (i.e., digestive tract), passed in stool and then sampled for laboratory testing. As bowel inflammation increases, so do FC levels. The commonly accepted normalrange for FC is a level of 50 µg/g or below, although this varies with age. FC levels are elevated in newborns, decline to a normal adult range by age five, then increase again in late adulthood (60+ years). FC testing is a useful tool for both diagnosing and managing IBD. As the test is sensitive to inflammation, doctors can use FC to differentiate between inflammatory conditions such as IBD, and non-inflammatory conditions such as irritable bowel syndrome (IBS). This is particularly useful given that these conditions can present with similar symptoms (e.g., abdominal pain, diarrhea). FC testing can also help in monitoring the condition after diagnosis. Similarly, FC testing can help doctors distinguish between an IBD-related flare-up and other forms of illness that may imitate IBD symptoms (e.g., bacterial infection). Because FC changes in proportion to the level of inflammation, test results can provide useful information regarding the changes in disease severity. An increase in FC levels may indicate a worsening in disease severity (i.e., an increase in gut inflammation), whereas low levels of FC suggests that the disease is inactive and that the current treatment is working.
Stool testing also can help with diagnosis by ruling out the presence of other infectious pathogens (e.g., bacteria, virus) that may be the cause of symptoms. Similarly, in cases of confirmed IBD, testing for other pathogens can help doctors distinguish between an IBD-related flare-up and other forms of illness that may imitate IBD symptoms (e.g., bacterial infection).