P0520Early identification of steroid non-responders in acute severe ulcerative colitis: external validation of the ASUC score and comparison with established prognostic models

Abstract Background Acute severe ulcerative colitis (ASUC) affects up to one quarter of patients with ulcerative colitis and carries substantial risk of colectomy. Early recog-nition of intravenous corticosteroid non-response is essential, yet most indices—such as the Oxford criteria—require reassessment on day 3, delaying rescue therapy. The ASUC score, based on admission albumin, C-reactive protein (CRP), endoscopic severity (Ul-cerative Colitis Endoscopic Index of Severity, UCEIS), and pre-admission steroid use, was recently proposed to predict non-response at admission. This study aimed to ex-ternally validate the ASUC score and compare its performance with established indices. Methods We performed a single-center retrospective validation study including con-secutive ASUC admissions (2015–2024). The primary outcome was corticosteroid non-response, defined as need for infliximab, ciclosporin, or colectomy. Model perfor-mance was assessed for discrimination (AUC, bootstrap-corrected 2,000 resamples), calibration (intercept, slope, Brier score), and clinical utility (decision-curve analysis). Comparator indices included ACE, ADMIT-ASC, Oxford day-3, Lindgren, and Edin-burgh. Predefined subgroup analyses evaluated infection and biologic exposure. Results Ninety-one admissions were analyzed; 18 (19.8 %) required rescue and 5 (5.5 %) underwent colectomy within 90 days. The ASUC score showed excellent discrimination (AUC 0.89, 95 % CI 0.81–0.95), good calibration (intercept 0.26, slope 1.29), and net clin-ical benefit across 30–50 % thresholds. At cut-off ≥ 2, sensitivity 94 % and specificity 78 % outperformed other indices (AUC 0.62–0.83). Subgroup analyses confirmed stable per-formance; the infected-only subgroup showed lower discrimination (AUC 0.71) Conclusion The ASUC score accurately identifies steroid non-responders on the day of admission, outperforming or matching established day-3 indices. Its simplicity and re-liability support its integration into early ASUC management to expedite rescue therapy and potentially improve outcomes. References: Rubin, D.T.; Ananthakrishnan, A.N.; Siegel, C.A.; Barnes, E.L.; Long, M.D. ACG Clinical Guideline Update: Ulcerative 373 Colitis in Adults. Am. J. Gastroenterol. 2025, 120, 1187–1224. 374 Moran, G.W.; Gordon, M.; Sinopolou, V.; Radford, S.J.; Darie, A.M.; Vuyyuru, S.K.; Alrubaiy, L.; Arebi, N.; Blackwell, J.; 375 Butler, T.D.; et al. British Society of Gastroenterology guidelines on inflammatory bowel disease in adults: 2025. Gut 2025, 376 *74 *(Suppl 2), s1–s101. Deloshaan, S.; Pradeep, K.R.; Dheeraj, S.; Hadi, M.; Maneesha, B.; Naveed, I.; Carolyn, M.; John, E.; Waled, M. P069 Admis-380 sion steroid use, serum albumin and endoscopic severity predict intravenous steroid failure in patients with acute severe 381 ulcerative colitis. Am. J. Gastroenterol. 2020, 115 (Suppl 1), S18. Conflict of interest: Dr. Mesquita, Pedro: No conflict of interest Pinho, Rolando: No conflict of interest Silva, João Carlos: No conflict of interest Costa, Catarina: No conflict of interest Teixeira, Pedro: No conflict of interest Ferreira, Rita: No conflict of interest Ponte, Ana: No conflict of interest