Magnetic Resonance Enterography as a Screening Tool for Axial Spondyloarthritis in Crohn's Disease: A Prospective Single-center Cross-sectional Observational Study Using MRE Screening Followed by Clinical Assessment

Spondyloarthritis (SpA) is a term that encompasses psoriatic arthritis with axial disease, ankylosing spondylitis and non-radiological axial spondyloarthritis. The prevalence of SpA in the general population is estimated to be between 0.01%-2.5%. SpA patients have a high burden of inflammatory bowel disease (IBD), which primarily includes Crohn's disease (CD) and Ulcerative colitis (UC), with an estimated prevalence of 10%-12%. However, few studies have investigated the converse; the presence of IBD cases with undiagnosed SpA. Untreated SpA may lead to a significant impact on general health and quality of life; therefore early diagnosis and treatment is crucial. Most CD patients will have had a MRE assessment for their CD, which also captures the axial skeleton and can therefore be used to screen for evidence of axial SpA (axSpA). In this study, MRE images from consenting CD subjects will be reviewed for evidence of axSpA. CD patients with evidence of axSpA will then be reviewed in a rheumatology clinic to assess more specifically for SpA. This will include completion of patient reported outcome measures, clinical examination, routine blood tests, human leucocyte antigen (HLA)-B27 genotyping and a dedicated axial magnetic resonance imaging (MRI) scan. The patients will also be consented to participate in the second part of the study which will be to compare these 'cases' statistically to a 'control' group of age- and sex-matched CD subjects without MRE evidence of axSpA.

This study aims to: (i) determine the validity, sensitivity and specificity of MRE as a screening tool for axSpA in CD patients using dedicated axial MRI scans with clinical assessment as the gold standard; (ii) devise an algorithm of clinical indices that can be used as a screening tool for axSpA in CD cases.