The interest in histology for ulcerative colitis (UC) arose recently. This systematic review and meta-analysis aims to assess, for the first time, whether histological outcomes are more informative than endoscopic and clinical in distinguishing the impact of intervention over placebo in induction trials.
MEDLINE, ScienceDirect and Cochrane Central Register of Controlled Trials were searched to identify randomized placebo-controlled trials (RCT) enrolling moderate-to-severe UC patients. Studies were assessed using the Quality Assessment Tool for Studies with Diverse Designs. We analyzed the pooled proportion of patients achieving clinical, endoscopic and histological remission and response after a pharmacological intervention and compared the results with those of placebo-treated patients using random-effects model.
From 889 identified records, 13 RCT were included. The odds ratio (OR) for remission was higher in patients receiving intervention than in those under placebo for clinical (OR 2.13, 95%CI 1.33-3.43), endoscopic (OR 1.46, 95%CI 0.19-11.18), and histological remission (OR 1.85, 95%CI 1.20-2.84). Significant differences were observed for all response outcomes (clinical: OR 2.27, 95%CI 1.84-2.85; endoscopic: OR 2.16, 95%CI 1.51-3.10; histological: OR 3.63, 95%CI, 1.41-9.36). No significant heterogeneity existed; no subgroup effects were found for duration of the induction or histological scale (p>.05). Clinical and histological remission and endoscopic response were concordant in discriminating interventions from placebo.
Histological outcomes are informative in trials of moderate-to-severe UC. Further studies analyzing histology at the end of induction are needed to confirm its relevance in distinguishing the efficacy of an intervention over placebo in comparison to clinical and endoscopic outcomes and to explore its prognostic value.

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