CHI3L1 and inflammatory bowel disease: Patients with active IBD have elevated YKL-40 concentrations in serum and feces compared to the controls or inactive disease (serum concentrations of 59 μg/L for both active Crohn disease (CD) (21-654 μg/L) and ulcerative colitis (UC) (26-258 μg/L) vs. 43 μg/L (20-124 μg/L) in healthy controls, P < 0.001), with closer correlation to disease activity in the UC than CD (52).