DYNAMIC-UC: Early qFIT and Calprotectin Change Predicting Relapse in Biologic-Naive Ulcerative Colitis

This is a prospective, observational cohort study conducted across multiple centers in China. Biologic-naive UC patients (Mayo Endoscopic Subscore ≥2) initiating conventional therapy (mesalazine or corticosteroids) will be enrolled. Stool samples for quantitative FIT (qFIT) and fecal calprotectin (FC) will be collected at Baseline (Week 0) , Week 2 (±3 days) , and Week 4 (±3 days) . Patients are classified at Week 2: Group A (Rapid Responders): Both qFIT \& FC decrease \>50% from baseline OR normalize. Group B (Slow/Non-Responders): Either qFIT or FC decrease ≤50%. The primary endpoint is the composite event rate (clinical relapse OR treatment escalation to biologics/JAK inhibitors) by Week 52 (±2 weeks) . Clinical relapse is defined as an increase ≥2 points in partial Mayo score (excluding endoscopy) with a rectal bleeding subscore ≥1 requiring therapy adjustment. Treatment escalation occurs per standardized criteria (steroid-refractoriness or dependence). Secondary endpoints include time-to-event, corticosteroid-free remission, mucosal healing at Week 52, predictive model performance (AUC, sensitivity, specificity), NNT calculation, and baseline predictors.