Background & Aims Endoscopy limited to the rectosigmoid colon is the standard technique used to measure endoscopic healing in ulcerative colitis (UC) clinical trials. We evaluated whether rectosigmoidoscopy adequately measures UC activity in the more proximal colon. Methods We analyzed data from a phase 2, placebo-controlled study that evaluated the efficacy and safety of etrolizumab in patients with moderate to severely active UC who had not responded to standard therapy. Central readers determined Mayo Clinic endoscopic subscores (MCSe) and ulcerative colitis endoscopic index of severity (UCEIS) scores from the rectosigmoid and proximal colon in videos of 331 examinations performed at baseline, week 6, and week 10. Rates of endoscopic healing (MCSe ≤ 1, MCSe = 0) and scores from rectosigmoidoscopy and colonoscopy analyses were compared among 239 examinations with endoscopic assessment proximal to the rectosigmoid colon. Results There was a high degree of correlation between findings from rectosigmoidoscopy vs colonoscopy in assessment of disease activity based on MCSe of 2 or higher (r = 0.84) or MCSe of 1 or higher (r = 0.96), or the UCEIS score (r = 0.92). In 230 of 239 videos, findings from rectosigmoidoscopy agreed with those from colonoscopy in the detection of active disease (MCSe ≥ 2; n = 205) or healing (MCSe ≤ 1; n = 25). In 9 videos (2 taken at baseline, 7 taken after treatment), colonoscopy found proximal disease activity not detected by rectosigmoidoscopy. Post-treatment discordance was more frequent in the placebo group, affecting assessment of efficacy at week 10. When endoscopic healing was defined as MCSe of 0, there were discordant findings from only 1 video. Conclusions There is a high degree of correlation in assessments of UC activity made by rectosigmoidoscopy vs colonoscopy. For detection of endoscopic healing (MCSe ≤ 1), colonoscopy found persistent proximal lesions in the placebo group, which affected efficacy analyses. When endoscopic healing was defined as MCSe of 0, the concordance between rectosigmoidoscopy and colonoscopy was nearly perfect.
- Inflammatory Bowel Disease
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