P162 Presence of extra-musculoskeletal manifestations increases the likelihood of magnetic resonance imaging identified axial inflammation: an analysis of real-world data

Abstract Background/Aims The spondyloarthritis (SpA) disease spectrum is characterised by overlapping clinical features, including extra-musculoskeletal manifestations (EMMs) with a varied prevalence of axial phenotype. In clinical practice, magnetic resonance imaging (MRI) is routinely utilised to identify axial involvement, due to its ability to detect lesions suggestive of active inflammation and structural damage at the spine and sacroiliac joints. Here, we use real-world data to explore the prevalence of axial spondyloarthritis (axSpA) as shown by MRI in people with back pain and to explore how the clinical phenotype, particularly the presence of EMMs, may influence the prevalence of MRI findings. Methods MRI scans of the spine and sacroiliac joints (SIJs) requested under the inflammatory back pain (IBP) protocol between May 2020 and December 2024 were identified as part of a retrospective service evaluation in a large teaching hospital. Data relating to MRI findings were extracted from the radiology report. Demographics (age, sex), HLA-B27 status, and data on pre-existing EMMs such as Psoriasis (PsO) without and with peripheral arthritis, inflammatory bowel disease (IBD) or uveitis were extracted from the electronic health records Results During the audit period, 1446 MRIs were requested to diagnose or exclude axSpA in 1412 patients (n = 34 had 2 scans). Of these, 498 MRIs were performed in patients with an associated EMM, mostly skin psoriasis (n = 389) of whom n = 174 had a pre-existing diagnosis of peripheral arthritis (PsA); followed by IBD (n = 89) and uveitis (n = 28). Eight patients had 1 EMM present. The rest (n = 948) were performed in individuals with back pain and clinical suspicion of axSpA with no EMMs. Overall, patients with any EMM were more likely to have evidence of axial involvement on MRI compared to those without (31.3% vs 22.0%). Amongst specific phenotypic features, MRI determined axial involvement was commonest in those with uveitis (60.7%) with similar prevalences found in those with concomitant skin PsO (31.6%), IBD (27.0%) or peripheral PsA (27.0%). Conclusion In patients with suspected axSpA, the presence of EMMs increases the likelihood of an MRI scan suggestive of axial involvement. Further work to improve identification and patient referral is warranted, particularly in those with EMMs present. Disclosure J. Weddell: None. R. Shah: None. S.R. Harrison: None. A. Barr: None. J. Freeston: None. C. Vandevelde: None. J. Fitton: None. K. Naraghi: None. D. McGonagle: None. H. Marzo-Ortega: None.