Background Among populations with ankylosing spondylitis (AS), the frequency and severity of extra-articular manifestations (EAMs) vary widely; due to underlying geographic and genetic differences, individual characteristics, and the impact of treatment with anti-tumour necrosis factor [TNF] agents. The frequency of EAMs among Canadians with AS has not previously been examined, using data from a large clinical registry.

Objectives To estimate the prevalence of EAMs, including uveitis, inflammatory bowel disease (IBD), dactylitis, and enthesitis, in a population of Canadians undergoing active management for AS.

Methods This retrospective study used RHUMADATA®, a multicentre registry developed by rheumatologists of the IRRM and Centre d'ostéoporose et de rhumatologie de Québec to evaluate the effectiveness and safety of rheumatologic therapies. Up to 15 years of real-world observational data on the broad set of patients treated in clinical practice are available. The proportion with EAMs was estimated according to type. The frequency of EAMs was compared according to age at cohort entry (≤40 vs >40 years), sex, AS severity (by BASDAI score), and status of treatment with anti-TNFs (anti-TNF-naive, anti-TNF treated [without switching], and anti-TNF treated [with switching]).

Results The mean (SD) age at cohort entry was 36.0 (12.6) years, and 60.0% were male. Of the 944 patients, 268 (28.4%) were ever diagnosed with an EAM over a median of 9.66 (10.58) years of follow-up. Prevalence was 14.7% for uveitis, 5.8% for IBD, 4.3% for dactylitis, and 9.0% for enthesitis (Table). The proportion with EAMs was: slightly higher among females versus males (31.0% vs. 26.7%), among older versus younger patients (29.5% vs. 25.9%), among those with more severe disease (from 29.2% [mild AS] vs. 34.1% [severe AS]), and among anti-TNF treated patients (18.8% [anti-TNF-naïve] to 47.0% [treated with anti-TNFs, with switching]).

Conclusions EAMs are common among Canadians with AS, occurring in up to 28% over almost 10 years of follow-up, with uveitis occurring the most frequently (in almost 15% of the cohort). EAMs were most frequent among those with more severe disease (in 34%) and among those treated with anti-TNFs (in 20–50% of such patients). These estimates are useful for comparing to other geographic areas, where the risk factor distribution for AS and its sequelae would differ; and for use in economic models to evaluate the benefits and costs of new therapies.

Disclosure of Interest S. Szabo: None declared, S. Chehab Employee of: Novartis Canada, L. Coupal Consultant for: Novartis, Speakers bureau: Novartis, D. Choquette: None declared