ObjectivesPredicting longer-term response to biological therapy for small bowel Crohn's disease (SBCD) is an unmet clinical need. Diffusion-weighted magnetic resonance (MR) imaging (DWI) may indicate disease activity, but its predictive ability, if any, is unknown. We investigated the prognostic value of DWI for 1 year response or remission (RoR) in SBCD patients commencing biologic therapy, including incremental value over C-reactive protein (CRP) and faecal calprotectin (FC).MethodsA subset of participants in a prospective, multicentre study investigating the predictive ability of motility MRI for 1-year RoR in patients starting biologic therapy for active SBCD, underwent additional DWI at baseline and post-induction (12-30 weeks). CRP and FC were collected in a subgroup. RoR at 1 year was evaluated using clinical and morphological MR enterography (MRE) parameters. We calculated sensitivity and specificity to predict RoR and quality of life (QoL) at 1 year, comparing apparent diffusion coefficient (ADC) value, Clermont score, and CRP using multivariable logistic regression.ResultsA total of 25 participants were included (mean 36.9 years, 32% female). ADC changes and Clermont score had poor sensitivity (30.0% [95% CI, 6.7-65.2] and 40.0% [95% CI, 12.2-73.8], respectively) and poor-to-modest specificity (50.0 [95% CI, 27.2-72.8] and 65.0% [95% CI, 40.8-84.6]) for RoR. None of Clermont score, CRP, or FC predicted QoL.ConclusionsDWI has inadequate sensitivity and specificity for RoR at 1 year. There is no significant incremental prognostic value of DWI over CRP and FC to predict RoR and/or QoL at 1 year.Advances in knowledgeEarly post-induction DWI has no prognostic value for RoR at 1 year.