Fecal calprotectin as a marker of inflammatory bowel diseases

Calprotectin is a calcium- and zinc-binding protein belonging to the S100 protein family. This protein is found mainly in the cytoplasm of neutrophils, and, to a lesser extent, in monocytes and macrophages, which can be found in any human organs, but mainly in blood, cerebrospinal fluid, feces, saliva, and synovial fluid. Calprotectin is an effective tool forthe differential diagnosis of inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS). There is a connection of fecal calprotectin (FC) with the endoscopic activity of IBD, however, the available literature shows significant differences in the sensitivity and specificity of FC for predicting the endoscopic activity of the disease. In addition, FC can be considered as a predictor of histological mucosal healing and as a marker for assessing the response to treatment, including surgical, but there is still no consensus on the threshold value of a biomarker for these purposes. Conflicting data are presented in reports on FC as a predictor of IBD recurrence. FC seems to be effective for detecting relapse, however, there is no specific threshold value, therefore, the marker cannot completely replace endoscopic examination methods. In addition, there is intraindividual variability in the concentration of FC in patients, depending on age, type of feeding in the first year of life, taking medications, which significantly complicates the interpretation of the results.