Abstract:Objective To explore the predictive value of fecal chitinase 3-like 1(CHI3L1) in predicting endoscopic activity and severity of ulcerative colitis.Methods A case-control study was conducted to compare the difference of fecal CHI3L1 between 183 ulcerative colitis patients and healthy controls from March 2017 to May 2019, and to analyze the correlation between fecal CHI3L1 and the Seo.m clinical activity index (CAI) of ulcerative colitis and the ulcerative colitis endoscopic index of severity (UCEIS). ROC curve was used to analyze the accuracy of fecal CHI3L1 in predicting endoscopic activity and severity of ulcerative colitis, and to determine the best diagnostic boundary point, sensitivity and specificity of diagnosis.Results The fecal CHI3L1 of ulcerative colitis patients was 75.91 (17.25, 834.72) ng/ml, which was significantly higher than that of healthy controls, was 5.17 (3.18, 16.45) ng/ml) (P < 0.05). There were statistically significant differences in fecal CHI3L1 and the three groups of Seo.m CAI (P < 0.05) and the three groups of UCEIS (P < 0.05). The fecal CHI3L1 level was positively correlated with Seo.m CAI and UCEIS (rs = 0.580 and 0.760, all P < 0.05). The area under ROC curve of fecal CHI3L1 level predicting endoscopic activity and severity UC was 0.929 (95% Cl: 0.877, 0.974) and 0.908 (95% Cl: 0.842, 0.965). When the fecal CHI3L1 > 15.28 ng/ml, it has highest accuracy in the diagnosis of endoscopic activity, the sensitivity and specificity were 93.25% (95% Cl: 0.895, 0.992) and 86.39% (95% Cl: 0.787, 0.914). When the fecal CHI3L1 >112.45ng/ml, the accuracy of diagnosing severity UC is the highest, the sensitivity and specificity were 87.92% (95% Cl: 0.802, 0.937) and 75.13% (95% Cl: 0.674, 0.863) respectively.Conclusions Fecal CHI3L1 is a better indicator to judge ulcerative colitis endoscopic activity and severe ulcerative colitis, it has high clinical application value in the evaluation of colonic mucositis degree in UC patients, and is one of the convenient and reliable non-invasive examination methods.