Diagnostic accuracy of magnetic resonance enterography and intestinal ultrasound for treatment response assessment in Crohn's disease (MANTRA): protocol for a multicentre, non-randomised, multiple-arm, prospective cohort comparison study.

introductionMR enterography (MRE) and intestinal ultrasound (IUS) are used to assess therapeutic response in Crohn's disease (CD) follow-up. There is, however, no clear guidance regarding which modality should be used for individual patients or if they are interchangeable. Therefore, clinical practice varies. We will compare the accuracy of MRE and IUS to classify treatment response in CD. METHODS AND ANALYSIS: Multicentre, non-randomised, multiple arm, prospective cohort study of luminal CD patients aged 16 years or older being treated with steroids, immunomodulators, biologics/biosimilars or small molecules with baseline MRE or IUS. The study will be based in three tertiary referral centres, UK (n=2) and Belgium (n=1), with a target sample size of 155 patients. Patients will undergo both MRE and IUS for response assessment within 20 months of baseline scanning, performed within 6 weeks of each other. One scan will be standard care, the other a research intervention. Interpreting radiologists will be masked to the alternative response assessment test. The primary outcome is the comparative accuracy of MRE and IUS for European Crohn's and Colitis Organisation-European Society of Gastrointestinal and Abdominal Radiology treatment response group categorisation compared with multidisciplinary consensus panel reference standard, using all available clinical information. Secondary outcomes include the influence of baseline scanning (MRE or IUS) on response characterisation accuracy, response accuracy of MRE and IUS disease activity scoring systems, management impact for each follow-up imaging modality and patient reported preferences. ETHICS AND DISSEMINATION: This protocol has been approved by the National Health Service Research Ethics Committee and West of Scotland Research Ethics Committee 1 (24/WS/0121). Participant informed written consent will be obtained. Findings will be disseminated by peer-reviewed publications, conference presentations and patient and public involvement collaborators. TRIAL REGISTRATION NUMBER: NCT06800326.