Baseline Data and Measurement Instruments Reported in Observational Studies in Inflammatory Bowel Disease: Results from a Systematic Review

Background: Heterogeneity in demographic and outcomes data with corresponding measurement instruments [MIs] creates barriers to data pooling and analysis. Several core outcome sets have been developed in inflammatory bowel disease [IBD] to homogenize outcomes data. A parallel Minimum Data Set [MDS] for baseline characteristics is lacking. We conducted a systematic review to develop the first MDS. Methods: A systematic review was made of observational studies from three databases [2000-2021]. Titles and abstracts were screened, full-text articles were reviewed, and data were extracted by two reviewers. Baseline data were grouped into ten domains: demographics, clinical features, disease behaviour/complications, biomarkers, endoscopy, histology, radiology, healthcare utilization and patient-reported data. Frequency of baseline data and MIs within respective domains are reported. Results: From 315 included studies [600 552 subjects], most originated from Europe [196; 62%] and North America [59; 19%], and were published between 2011 and 2021 [251; 80%]. The most frequent domains were demographics [311; 98.7%] and clinical [289; 91.7%]; 224 [71.1%] studies reported on the triad of sex [306; 97.1%], age [289; 91.7%], and disease phenotype [231; 73.3%]. Few included baseline data for radiology [19; 6%], healthcare utilization [19; 6%], and histology [17; 5.4%]. Ethnicity [19; 6%], race [17; 5.4%], and alcohol/drug consumption [6; 1.9%] were the least reported demographics. From 25 MIs for clinical disease activity, the Harvey-Bradshaw Index [n=53] and Mayo score [n=37] were most frequently used. Conclusions: Substantial variability exists in baseline population data reporting. These findings will inform a future consensus for MDS in IBD to enhance data harmonization and credibility of real-world evidence.