Researchers Assess Associations of EAMs With Arthritic Conditions

Anterior uveitis (AU) is the extra-articular manifestation (EAM) most strongly associated with ankylosing spondylitis (AS) and undifferentiated spondyloarthritis (uSpA), Swedish researchers reported, while the association of these EAMs with psoriatic arthritis (PsA) was weak.

The investigators set out to estimate the incidence and strength of association of anterior uveitis (AU), inflammatory bowel disease (IBD), and psoriasis (PsO) in patients with AS, uSpA, and PsA, compared with controls.

The team identified 3 cohorts of patients aged 18–69 years in the Swedish National Patient Register during the period 2001–2015. Of these patients, 8517 had AS; 10,245 had uSpA, and 22,667 had PsA. The groups were mutually exclusive.

Controls matched for age, sex, and geography were identified from the Swedish Population Register. These patients were followed beginning January 1, 2006, or 6 months after the first SpA diagnosis, whichever occurred later. For each EMA under study, the team calculated incidence rates (IRs) and incidence rate ratios according to age and sex.

“Incidence rate ratios for incident AU, IBD, and psoriasis were significantly increased in AS (20.2, 6.2, 2.5), uSpA (13.6, 5.7, 3.8) and PsA (2.5, 2.3, n.a) vs controls,” the authors wrote. “Men with AS and uSpA had significantly higher IRs per 1000 person-years at risk for incident AU than women with AS (IR 15.8 vs 11.2) and uSpA (IR 10.1 vs 6.0), whereas no such sex difference was demonstrated in PsA or for the other EAMs.”

They concluded, “AU, followed by IBD and psoriasis, is the EAM most strongly associated with AS and uSpA. Among the SpA subtypes, AS and uSpA display a largely similar pattern of EAMs, whereas PsA has a considerably weaker association with AU and IBD.”

--Rebecca Mashaw

Reference:

Bengtsson K, Forsblad-d'Elia H, Deminger A, et al. Incidence of extra-articular manifestations in ankylosing spondylitis, psoriatic arthritis and undifferentiated spondyloarthritis: results from a national register-based cohort study. 2021. Rheumatology; 60(6): 2725–2734 https://doi.org/10.1093/rheumatology/keaa692