Early axial spondyloarthritis versus established disease: a single-center analysis based on the new ASAS definition of early disease.

Abstract

Objectives: The applicability of the new Assessment of Spondyloarthritis International Society (ASAS) consensus definition of early axial spondyloarthritis (axSpA) has barely been tested in clinical settings. We aimed to check the applicability of this new definition in a real clinical context.

Methods: Single-center cross-sectional study involving 330 consecutive patients fulfilling axSpA criteria. Similarities and differences between patients with early (according to the new ad hoc definition) and established disease were analyzed. Logistic regression models adjusted for sex and exposure to biologic therapies were constructed to analyze the different disease outcomes between both subpopulations.

Results: Of 299 patients for whom information on defining characteristics of early axSpA could be reliably collated, 45 (15%) met the ASAS definition of early axSpA, median disease duration of 1.0 year [IQR, 1.0-2.0]. Compared to established disease, these patients were younger (p = 0.001), with a similar male-to-female ratio, and a higher exposure to NSAIDs (p = 0.015) but lower to biologics (p = 0.005). Uveitis prevalence was similar between both groups (early, 15.6% and established, 16.1%). Regardless of sex and biologic therapy, inflammatory burden, disease activity and the impact on quality of life were similar in both groups. As expected, structural damage was higher among established cases. Also, regardless of disease duration and exposure to biologic therapies, men had better disease outcomes than women.

Conclusion: Patients with early axSpA present similarities and differences with respect to established cases. The new ASAS definition of early disease may be applicable in real-world clinical settings.

Key points: • Patients with early axial spondyloarthritis show similarities and differences with respect to established cases. • The overall burden of disease is similar in both subgroups of patients with axial SpA. • In both study groups, men showed better disease outcomes than women. • The new ASAS definition of early axial spondyloarthritis is applicable in real-life clinical settings.