Assessment of outcomes in Crohn's disease: A systematic review of randomized clinical trials to inform a multiple outcome framework

Longstanding disease control in Crohn's disease (CD) is challenging and requires understanding treatment efficacy and outcomes assessment. With multiple novel therapeutic options, rigorous evaluation of outcomes in randomized controlled trials (RCTs) is crucial to inform clinical practice. This study systematically reviewed RCTs focusing on CD outcomes to elucidate the breadth and depth of reported outcomes and measurement instruments. A systematic search was conducted on MEDLINE and Scopus for RCTs published from 1 January 2000 to 31 January 2023. Eligible studies included full-text articles with at least 50 adult CD patients. Primary and secondary outcomes, along with their measurement instruments, were categorized according to the Outcome Measures in Rheumatology Filter 2.1 framework. From 88 included studies, 393 outcomes were analyzed. Clinical outcomes, such as clinical remission and response, were the most prevalent (50.6%); biomarkers (11.5%) and patient-reported outcomes (10.2%) were also assessed. Other outcomes included disease behavior and complications (2%), endoscopy (10.4%), histology (0.5%), radiology (1.3%), healthcare utilization (3.8%), and therapy-related safety (6.9%). Composite outcomes showed an increasing trend, reflecting a shift toward comprehensive evaluations. Coprimary endpoints, including clinical symptoms and mucosal inflammation, were reported in 21 of 88 studies. This review highlights the evolving landscape of outcome assessment in CD RCTs, emphasizing the increasing complexity of outcomes. The prominence of composite outcomes underscores efforts to capture the multidimensional nature of CD. These findings will inform the second stage of a two-round e-Delphi aimed at prioritizing key domains and outcomes for developing a multiple-component outcome for RCTs in CD research.