Calprotectin is a calcium and zinc-binding protein that belongs to the S100 family and is very abundant in the cytosol of neutrophils. It is involved in many physiological functions, including cell differentiation, immune regulation, tumorigenesis, apoptosis, and it plays a major role during inflammation. Fecal calprotectin serves as a sensitive marker for inflammation in the gastrointestinal tract and is useful for differentiating inflammatory bowel disease (IBD) from irritable bowel syndrome (IBS). Its levels can be quantitively measured using a two-site sandwich ELISA or CLIA assay.