P0435 CDAS-QoL Thresholds for Surgical Decision-Making in Crohn’s Disease Anorectal Stricture: A Diagnostic Accuracy Study

Abstract Background Anorectal stricture is a highly disabling complication of perianal Crohn’s disease (CD), affecting about 17%–22% of patients, of whom approximately 57% eventually require stoma formation or rectal resection1,2. Surgical decision-making for anorectal stricture still relies largely on symptoms and anal canal diameter and currently lacks standardized quantitative thresholds3. The Crohn’s Disease Anorectal Stricture Quality of Life (CDAS-QoL) scale, developed and psychometrically validated in our centre, is a patient-reported outcome measure that captures multidimensional functional limitations and health-related quality of life4. In this study, we apply diagnostic accuracy methods to relate CDAS-QoL scores to surgical indications and to define a data-driven “surgical warning threshold” to support risk stratification and clinical decision-making. Methods We conducted a single-centre diagnostic accuracy study in a retrospectively assembled real-world cohort of patients with CD–related anorectal stricture who presented between 2016 and 2025. The CDAS-QoL score was prespecified as the index test, and multidisciplinary team consensus on the need for surgery, based on symptoms, anal canal calibre and imaging, served as the reference standard. Receiver operating characteristic analysis, the Youden index and a sensitivity-prioritised rule were used to define a CDAS-QoL “surgical warning threshold”, which was internally validated by bootstrap resampling (1000 iterations) and decision curve analysis. Results Of 221 patients with CD–associated anorectal stricture, 57 (25.8%) underwent CD-related transanal surgery after completing the CDAS-QoL. Baseline CDAS-QoL scores were higher in patients who subsequently had surgery than in those managed conservatively (85 [81, 89] vs 62 [54, 73], p < 0.001). CDAS-QoL showed good discrimination for MDT-defined need for surgery (AUC 0.89; SE 0.02; 95% CI 0.85–0.93; p < 0.001). A “surgical warning” cut-off of 78.5 yielded a sensitivity of 0.93 and specificity of 0.81, corresponding to positive and negative likelihood ratios of 4.92 and 0.09, respectively. Using this threshold, 84/221 patients (38.0%) were classified into a high-risk “red zone” and 137/221 (62.0%) into a lower-risk “green zone”. Bootstrap validation (B = 1000) confirmed similar sensitivity (0.93), specificity (0.81) and accuracy (0.84) at this cut-off, and decision-curve analysis showed higher net benefit than “treat-all” or “treat-none” strategies for thresholds of 3–25%. Conclusion For patients with CD anorectal stricture, CDAS-QoL–based thresholds may help identify those with major functional impairment and provide a practical cut-off to guide surgical treatment and support shared decision-making. References: 1. Bouguen G, Trouilloud I, Siproudhis L et al. Long-term outcome of non-fistulizing (ulcers, stricture) perianal Crohn’s disease in patients treated with infliximab. Aliment Pharmacol Ther. 2009;30(7):749-56 2. Yamamoto T, Allan RN, Keighley MR. Effect of fecal diversion alone on perianal Crohn’s disease. World J Surg. 2000;24(10):1258-62; discussion 1262-3 3. Lightner AL, Click B, Yamamoto T, Spinelli A, Kotze P. Management of Isolated Anal Strictures in Crohn’s Disease. Dis Colon Rectum. 2020;63(12):1639-1647 4. Li JR, Yang BL, Zhu ZX et al. Development and psychometric validation of a patient-reported outcome measure scale for Crohn’s disease anorectal stricture. J Crohns Colitis. 2025;19(5) Conflict of interest: Dr. Li, Jinrong: No conflict of interest Shuhui, Zhan: No conflict of interest Chenchen, Shan: No conflict of interest Ning, Ding: No conflict of interest Xinyu, Yang: No conflict of interest Ying, Sun: No conflict of interest Wenjie, Guo: No conflict of interest Yuxia, Gong: No conflict of interest Zhu, Ping: No conflict of interest Weiming, Zhu: No conflict of interest