POS0035 ONE IN TWENTY INFLAMMATORY BOWEL DISEASE PATIENTS WHO UNDERWENT ABDOMINOPELVIC COMPUTED TOMOGRAPHY HAVE UNDIAGNOSED AXIAL SPONDYLOARTHRITIS
Authors: C. S. E. Lim, L. Hamilton, S. Low, A. Toms, A. Macgregor, K. Gaffney
Journal: Annals of the Rheumatic Diseases (2021)

Background: The diagnosis of axial spondyloarthritis (axSpA) is challenging and hindered by delay. There may be an opportunity to identify sacroiliitis for further rheumatology review in inflammatory bowel disease (IBD) patients who undergo Computed Tomography (CT) for non-musculoskeletal (MSK) indications. Objectives: To identify what proportion of IBD patients who underwent abdominopelvic CT for non-MSK indications have axSpA and to explore the role of an imaging strategy for identifying axSpA. Methods: Abdominopelvic CT scans of verified IBD patients were identified retrospectively from eight years of imaging archive. Patients between 18-55 yrs. were selected as having the highest diagnostic yield for axSpA. CT review (using criteria from a validated CT screening tool developed by Chan 1 ) was undertaken by a trained radiology team for presence of CT-defined sacroiliitis (CTSI). All CTSI patients were sent a screening questionnaire. Those with self-reported chronic back pain (CBP), duration &gt; 3 months, onset &lt; 45 years were invited for rheumatology review. This included a medical interview, physical examination (joint count, MASES, dactylitis count, BASMI), patient reported outcomes (BASDAI, BASFI, BASGI, Harvey-Bradshaw-Index, Partial-Mayo-Index), relevant laboratory tests (CRP, ESR, HLA-B27), axSpA protocol MRI, and remote review by a panel of experienced rheumatologists with a special interest in axSpA. Results: CTSI was identified in 60 of 301 patients. Thirty-two (53%) responded to the invitation to participate and 27 (84%) were enrolled. Of these, eight had a pre-existing axSpA diagnosis and five did not report chronic back pain. Fourteen patients underwent rheumatological assessment; three of 14 (21.4% [95% CI: 4.7%, 50.8%]) had undiagnosed axSpA. In total, 11 of 27 (40.7% [95% CI: 22.4%, 61.2%]) patients had a rheumatologist verified diagnosis of axSpA. Conclusion: One in five patients (60/301) with IBD who underwent abdominopelvic CT for non-MSK indications have CTSI and at least one in five (11/60) have axSpA. Five percent (3/60) were previously undiagnosed. This highlights a hidden disease burden and a potential strategy for identifying new cases. References: [1]Chan J, Sari I, Salonen D, Inman RD, Haroon N. Development of a Screening Tool for the Identification of Sacroiliitis in Computed Tomography Scans of the Abdomen. J Rheumatol 2016; 43(9); 1687-94. Acknowledgements: We are indebted to Baljeet Dhillon and Shin Azegami for their assistance in the scoring of the CTSI. Disclosure of Interests: Chong Seng Edwin Lim Grant/research support from: AbbVie, Louise Hamilton: None declared, Samantha Low: None declared, Andoni Toms: None declared, Alex MacGregor: None declared, Karl Gaffney Speakers bureau: AbbVie, Eli Lilly, Novartis, UCB Pharma, Consultant of: AbbVie, Eli Lilly, Novartis, UCB Pharma, Grant/research support from: AbbVie, Gilead, Eli Lilly, Novartis, UCB Pharma.