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.