Disease activity trajectories in early axial spondyloarthritis: results from the DESIR cohort

Background Disease activity may change over time in axial spondyloarthritis (axSpA). The objectives were to identify patterns of disease activity evolution in patients with early axSpA. Methods Patients from the prospective early axSpA cohort (DEvenir des Spondyloarthrites Indifferenciees Recentes (DESIR)) who fulfilled the Assessment in SpondyloArthritis Society (ASAS) criteria for axSpA at baseline and with at least three Ankylosing Spondylitis Disease Activity Score (ASDAS) values available over the 3 years of follow-up were analysed. Statistical analyses: trajectories were estimated by group-based trajectory modelling; predisposing baseline factors for such trajectories were identified by univariate and multivariable multinomial (logit) regression; work disability over time was compared between the trajectories by Cox hazard model. Results In all, 370 patients were analysed: mean disease duration was 1.6 (+/- 0.9) years. The five distinct trajectories of disease activity over the 3 years were (t1) `persistent moderate disease activity' (n=134 (36.2%)); (t2) `persistent inactive disease' (n=66 (17.8%); (t3) `changing from very high disease activity to inactive disease' ((n=29 (7.8%)); (t4) `persistent high disease activity' (n=126 (34.1%)) and (t5) `persistent very high disease activity' (n=15 (4.1%)). After adjustment for other characteristics, t2 was associated with a white-collar job (OR=2.6 (95% CI 1.0 to 6.7)) and t3 with male gender (OR=7.1 (1.6 to 32.2)), higher education level (OR=9.4 (1.4 to 63.4)) and peripheral joint involvement (OR=6.2 (1.23 to 31.32)). Patients from (t4) and (t5) were more often declared work disabled over follow-up (HR=5.2 (1.5 to 18.0) and HR=8.0 (1.3 to 47.9), respectively). Conclusions Trajectory modelling of disease activity was feasible in early axSpA: more than 30% patients (141/370) were in a trajectory with a persistent high disease activity. Persistent high disease activity trajectories were significantly associated with consequences on work.