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Introduction Spondyloarthritis (SpA), including ankylosing spondylitis (AS) and enteropathic arthritis (EA), are considered as the commonest extra-intestinal manifestation (EIM) of inflammatory bowel disease (IBD). However, their estimated prevalence varies significantly (range 1-46%) due to limited numbers and heterogenous disease definitions utilised across published studies. 1 Here we present data on the prevalence of AS and EA in IBD and their clinical associations from a large national cohort study.Methods The UK National Institute for Health and Care Research (NIHR) IBD BioResource (IBDBR)2 dataset is a cross-sectional study recruiting participants with diagnosed or suspected IBD at over 100 hospitals across the UK between 2016 and 2025. Baseline phenotypic data were collected by case note review at enrolment. Participants with unconfirmed IBD or missing inflammatory arthritis data were excluded from the current analysis. Unadjusted odds ratios (OR) with 95% confidence intervals were calculated to investigate clinical and phenotypic associations with the presence of SpA. Significant associations were incorporated into a multivariable model and non-significant associations (p<0.01) removed on a stepwise basis.Results Data from 38699 participants were analysed. Diagnosis of AS was reported in 1005 (2.1%) and EA in 2574 (5.5%), with both AS and EA present in 206 (0.4%). AS and EA were both associated with Crohn’s disease (CD), hospital admission for smoking, family history of IBD. serious infection and the presence of any non-musculoskeletal (MSK) EIM ( table 1). AS was also associated with IBD onset >40, being male and being ‘White or White British’. EA was associated with female sex. In a multivariable model, AS and EA were each associated with CD, smoking, serious infection and presence of any non-MSK EIM. EA was also associated with admission to hospital due to IBD and being female, whereas AS was associated with being male and IBD onset >40.Conclusions In this large multicentre dataset, the prevalence of EA and AS in IBD is lower than often reported in the literature. Both EA and AS are associated with sex, smoking, CD and other EIMs suggesting shared genotypic underpinning. EA also appears to be associated with a more aggressive phenotype of IBD with more hospital admissions. Further research including genetic analysis is needed to identify biomarkers of disease, severity and predictors of treatment response in the at risk IBD population.References Schwartzman M, et al. Spondyloarthritis in inflammatory bowel disease cohorts: systematic literature review and critical appraisal of study designs. RMD Open. 2022;8(1):e001777.Parkes M, IBD BioResource Investigators. IBD Bioresource: an openaccess platform of 25000 patients to accelerate research in Crohn’s and colitis. Gut 2019;68:1537–1540.Abstract P196 Table 1Summary of demographics and variables associated with a diagnosis of spondyloarthritisOverall (n=47056)Enteropathic arthritis (n=2574)Odds ratio for enteropathic arthritisAnkylosing spondylitis (n=1005)Odds ratio for ankylosing spondylitisCrohn’s disease [total]23240 (49.4%)1635 (63.5%)1.81 (1.67 – 1.97)631 (62.8%)1.75 (1.53- 1.99)UC/ IBD-U [total]23816 (50.6%)939 (36.5%)374 (37.2%)Male [n(%)]22889 (48.6%)874 (34.0%)0.53 (0.49- 0.58)546 (54.3%)1.26 (1.11 – 1.43)‘White or White British’ [n(%)]42263 (89.8%)2325 (90.3%)0.97 (0.82- 1.14)915 (91.0%)1.53 (1.16 -2.07)Onset of IBD>40 [n(%)]15295 (32.5%)813 (31.6%)1.05 (0.96- 1.15)396 (39.4%)1.35 (1.19- 1.54)Ever admitted to hospital due to IBD? [n(%)]22125 (47.0%)1528 (59.4%)1.66 (1.53 – 1.80)528 (52.5%)1.25 (1.10-1.42)Serious infection [n(%)]2213 (4.7%)241 (9.4%)1.81 (1.57 – 2.08)83 (8.3%)1.85 (1.46- 2.32)Current or previous smoker [n(%)]20878 (44.4%)1305 (50.6%)1.27 (1.16 -1.37)642 (53.9%)1.48 (1.30 – 1.68)Family History of IBD [n(%)]12724 (27.0%)792 (30.8%)1.21 (1.11- 1.32)311 (30.9%)1.21 (1.06 – 1.39)Any non-MSK EIM (psoriasis, iritis, erythema nodosum or primary sclerosing cholangitis) [n(%)]4334 (9.2%)673 (26.1%)3.48 (3.16- 3.83)294 (29.3%)4.30 (3.74- 4.94)UC: Ulcerative Colitis; IBD-U: Unclassified Inflammatory Bowel Disease; MSK: musculoskeletal; EIM: Extra-Intestinal Manifestation