ALPI and irritable bowel syndrome: Other fecal biomarkers: Numerous other fecal markers have been studied for IBD, including polymorphonuclear neutrophil (PMN)-elastase [232], neutrophil gelatinase-associated lipocalin (NGAL) (also known as lipocalin-2) [220,241], intestinal alkaline phosphatase (IAP) [220], and M2-pyruvate kinase (M2-PK) [244], among others.