Objective:To investigate the correlations of endoscopic evaluation results with laboratory indices and clinical disease activity in Crohn disease (CD) patients with different intestinal involvement.Methods:Data of 147 patients diagnosed as having CD who visited the Department of Gastroenterology, Zhongnan Hospital of Wuhan University from July 1, 2017 to June 30, 2022 were collected retrospectively. According to the involvement of intestinal segment, patients were divided into three groups: the group with isolated small intestinal involvement ( n=55), the group with both small intestinal and large intestinal involvement ( n=48), and the group with isolated large intestinal involvement ( n=44). Correlations of endoscopic evaluation (based on CDEIS) with laboratory indices and clinical disease activity (based on Harvey-Bradshaw index) were analyzed. Results:C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) could be used for the prediction of endoscopic disease activity. The areas under curve (AUC) of receiver operator characteristic (ROC) were 0.677 (0.506-0.849) and 0.744 (0.597-0.890), respectively. In terms of determing clinical disease activity, clinical Harvey-Bradshaw index was consistent with endoscopic CDEIS score in 65.3% (96/147) patients, showing a low positive correlation ( r=0.260, P<0.05). In subgroup analysis for patients with isolated small intestinal involvement, CRP showed no predictive value for clinical disease activity [AUC (95% CI): 0.617 (0.461-0.773), P=0.148], while for endoscopic activity neither CRP nor ESR showed predictive value [AUC (95% CI): 0.537 (0.146-0.929), P=0.829; AUC (95% CI): 0.571 (0.153-0.990), P=0.680]. Furthermore, for patients with isolated small intestinal involvement and both small intestinal and large intestinal involvement, no correlation was found between clinical Harvey-Bradshaw index and endoscopic CDEIS score ( r=0.222, P=0.092; r=0.142, P=0.322). Conclusion:For CD patients with small intestinal involvement, especially isolated small intestinal involvement, laboratory indices and clinical disease activity cannot accurately reflect endoscopic disease activity. Great importance should be attached to evaluation of the extent and activity of intestinal lesions by endoscopy, especially enteroscopy.