Is it always necessary to wait until day 5 for second line treatment in children with acute severe ulcerative colitis?

BACKGROUND: ECCO-ESPGHAN guidelines for pediatric acute severe ulcerative colitis (ASUC) recommend delaying second-line therapy until day 5 of intravenous corticosteroids (IVCS). AIMS: To identify early clinical predictors of IVCS failure in pediatric ASUC and evaluate whether day 3 PUCAI could support earlier treatment escalation. METHODS: This multicenter retrospective study included biologic-naïve children hospitalized for ASUC between 2015 and 2024. Demographic, clinical, laboratory, and treatment data at diagnosis and during hospitalization were retrieved. Logistic regression identified predictors of IVCS failure, while ROC analysis evaluated day 3 PUCAI performance. RESULTS: Ninety-one patients were included (44.6% male; median age 13.3 years); 45 (49.5%) required second-line therapy. IVCS failure was less frequent in ASUC at diagnosis than during disease flare (37.0%vs 71.1%;p = 0.001). ASUC during disease flare was associated with higher odds of IVCS failure, although statistical significance was not reached (aOR 3.39, 95%CI 0.99-11.9;p = 0.051). In flare-ASUC patients, day 3 PUCAI ≥50 predicted IVCS non-response (94.1% specificity, 75.0% sensitivity, positive likelihood ratio of 12.8). Patients with PUCAI ≥50 had lower colectomy-free rates and probability of achieving clinical remission (p < 0.05). CONCLUSIONS: A day 3 PUCAI ≥50 in children with flare-ASUC may warrant earlier risk stratification and preparation for potential second-line rescue therapy.