Calprotectin gelangt in das intestinale Lumen durch:

1. Aktive Sekretion
2. Zell Beschädigungen
3. Zelltod

Dies führt zu erhöhten Calprotectinkonzentrationen im Stuhl. Dieser kann analytisch nachgewiesen werden. Erhöhte Konzentrationen zeigen damit die Wanderung von neutrophiler Granulozyten in die intestinale Mucosa auf Grund eines Entzündungsprozesses an. Patienten mit einer akuten chronisch entzündlichen Darmerkrankung (inflammatory bowel diseases (IBD)) wie Colitis ulcerosa oder Morbus Chron ist der Fäkale Calprotectin-Spiegel um das 10fache erhöht. Die Bestimmung dieses Werts kann zur Diagnose der genannten Erkrankungen dienen.

Although a relatively new test, faecal calprotectin is regularly used as an indicator for IBD during treatment, and as a diagnostic marker.^[8] Faecal calprotectin tests can also function in distinguishing patients with irritable bowel syndrome from those with IBD.^[1][6] Calprotectin is useful as a marker, as it is resistant to enzymatic degradation, and can be easily measured in faeces.^[19] Although faecal calprotectin correlates significantly with disease activity in people with confirmed IBD,^[20] elevated faecal calprotectin can be a false-positive indicator of IBD under some conditions. Importantly, intake of proton pump inhibitor is associated with significantly elevated calprotectin values.^[21] Furthermore, positive faecal calprotectin does not help in localizing IBD, or in distinguishing ulcerated colitis from Crohn disease.^[1] Faecal calprotectin can also indicate other gastrointestinal conditions such as colorectal cancer, gastroenteritis, and food intolerance.^[1] Calprotectin levels vary depending on age, comorbidity, and may vary day-to-day within individuals.^[1] Faecal calprotectin could be used as a preliminary screen in otherwise functional patients suspected of having IBD, or as a means of following mucosal healing.^[1] The potential for using faecal calprotectin in this way is debated, however, and cut-off levels have not been agreed upon.^[1]