Inter-observer variability for detection of suspected ileocolonic Crohn’s disease with magnetic resonance enterography

Background: Magnetic resonance enterography (MRE) can visualize Crohn's disease (CD) and its complications. Purpose: To determine the inter-observer agreement for the detection of ileocolonic CD. Material and Methods: This post-hoc analysis included MRE scans from 48 patients selected from a prospective, blinded multicenter study of patients with suspected CD. Based on ileocolonoscopy in the main study, CD was diagnosed in 39 (81%) patients, with colonic involvement in 36 (69%). Two senior radiologists and two junior doctors undergoing specialist training, blinded to clinical data assessed the image quality, CD presence, and disease severity. Results: The inter-observer agreement for CD detection varied by location: terminal ileum (κ = 0.77, 95% confidence interval [CI] = 0.63–0.89), colon (κ = 0.59, 95% CI = 0.42–0.74), and ileocolon (κ = 0.65, 95% CI = 0.49–0.80). Agreement was higher among senior radiologists than juniors: terminal ileum (κ = 0.83 vs. 0.73; P = 0.60) and colon (κ = 0.73 vs. 0.41; P = 0.11), though differences were not statistically significant. The inter-observer agreement for disease severity was poor to moderate with intraclass correlation coefficients (ICCs) of 0.51 (95% CI = 0.35–0.67) for the MaRIA and 0.46 (95% CI = 0.29–0.62) for the simplified MaRIA. Senior radiologists showed higher consistency, with moderate to good agreement: ICC of 0.69 for the MaRIA, 0.70 for the simplified MaRIA, and 0.80 for bowel wall thickness. Conclusion: In early CD, MRE demonstrated moderate to substantial inter-observer agreement for ileocolonic evaluation. Limitations in colonic assessment likely reflect early disease detection rather than observer variability, highlighting the need for a complementary assessment.