Background The prevalence of extra-articular manifestations (EAMs), i.e. acute anterior uveitis (AAU), psoriasis and inflammatory bowel disease (IBD), is strongly increased in patients with AS compared with the general population. However, epidemiological data on the occurrence of EAMs in AS are only based on cross-sectional studies, and previous estimates were not adjusted for a wide range of potential confounders.
Objectives To determine the incidence rates and relative risks of EAMs in patients with AS compared with population based controls and to describe the timing of onset and hazard patterns of EAMs along the course of AS.
Methods All incident patients with AS from the UK Clinical Practice Research Datalink (CPRD, 1987-2012) were matched with up to seven control subjects without AS by year of birth, sex, calendar time and practice. CPRD is the world's largest primary care database and representative of the total UK population. The date of first appearance of diagnosis of AS defined the index date. Control patients were assigned the same index date as their matched patient. In three sub-cohorts for each EAM, every patient was followed from his index date until either the first occurrence of the EAM-outcome of interest or until the end of CPRD follow-up. Incidence rates, cumulative incidence rates and cox-regression estimated adjusted (adj.) hazard ratios (HR) for the development of EAMs were calculated, with time-dependent adjustments for age, sex, comorbidity and medication use.
Results In total, 4,101 patients with AS (mean age at index date 43.7 years, 70.6% male, median duration of follow-up 5.4 years) were matched with 28,591 control subjects. At the index date, the proportion of patients with an EAM was 11.4% for AAU, 4.4% for psoriasis and 3.7% for IBD. Incidence rates of EAMs were 8.9/1,000 person-years for AAU, 3.4/1,000 person-years for psoriasis and 2.4/1,000 person-years for IBD in AS. The 20-year cumulative incidence was 24.5%, 10.1% and 7.5%, respectively. Risks of EAMs were 1.5- to 16-fold increased versus controls, with an adj. HR of 15.5 (95% CI, 11.6-20.7) for AAU, adj. HR of 1.5 (95% CI, 1.1-1.9) for psoriasis and adj. HR of 3.3 (95% CI, 2.3-4.8) for IBD. Risks of EAMs were higher in men than in women. The risks for all EAMs were highest in the first year after diagnosis. While the risk of AAU was still 9-fold increased 10 years after the index date, the risk had dropped to baseline levels after 5 years for psoriasis and after 10 years for IBD.
Conclusions The risk of in particular AAU, but also of psoriasis and IBD, is significantly increased in patients with AS compared with population controls. Hazard patterns are different for each of the EAMs.
Disclosure of Interest : None declared