A Narrative Systematic Review and Categorisation of Outcomes in Inflammatory Bowel Disease to Inform a Core Outcome Set for Real-world Evidence

Background Heterogeneity exists in reported outcomes and outcome measurement instruments [OMI] from observational studies. A core outcome set [COS] for observational and real-world evidence [RWE] in inflammatory bowel disease [IBD] will facilitate pooling large datasets. This systematic review describes and classifies clinical and patient-reported outcomes, for COS development. Methods The systematic review of MEDLINE, EMBASE, and CINAHL databases identified observational studies published between 2000 and 2021 using the population exposure outcome [PEO] framework. Studies meeting eligibility criteria were included. After titles and abstracts screening, full-text articles were extracted by two independent reviewers. Primary and secondary outcomes with corresponding OMI were extracted and categorised in accordance with OMERACT Filter 2.1 framework. The frequency of outcomes and OMIs are described. Results From 5854 studies, 315 were included: 129 [41%] Crohn’s disease [CD], 60 [19%] ulcerative colitis [UC], and 126 [40%] inflammatory bowel disease [IBD] studies with 600 552 participants. Totals of 1632 outcomes and 1929 OMI were extracted mainly from medical therapy [181; 72%], surgical [34; 11%], and endoscopic [6; 2%] studies. Clinical and medical therapy-related safety were frequent outcome domains recorded in 194 and 100 studies. Medical therapy-related adverse events [n = 74] and need for surgery [n = 71] were the commonest outcomes. The most frequently reported OMI were patient or event numbers [n = 914], Harvey-Bradshaw Index [n = 45], and Montreal classification [n = 42]. Conclusions There is substantial variability in outcomes reporting and OMI types. Categorised outcomes and OMI from this review will inform a Delphi consensus on a COS for future RWE in IBD. Data collection standardisation may enhance the quality of RWE applied to decision-making.