In search of a window of opportunity in axial spondyloarthritis: treatment outcomes across different symptom durations

Objectives This study aimed to determine the effectiveness of a first tumour necrosis factor inhibitor (TNFi) in patients with short and long symptom duration in axial spondyloarthritis (axSpA), using alternative cut-offs for back pain duration: ≤1 year as very early, >1 year, and ≤5 years as intermediate axSpA, and >5 years as late axSpA. Methods A total of 1161 patients with axSpA from the Swiss Clinical Quality Management registry, who had data on the duration of back pain and initiated their first TNFi, were included. Patients were categorised as follows: very early axSpA ( N = 138), intermediate axSpA ( N = 329), and late axSpA ( N = 694). Adjusted logistic regression models were used to compare the likelihood of achieving a low disease activity status (Axial Spondyloarthritis Disease Activity Score [ASDAS] <2.1) at 1 year, adjusting for age, sex, human leucocyte antigen-B27, educational level, body mass index, ASDAS, current smoking, and presence of inflammation on magnetic resonance imaging of the sacroiliac joints. Drug survival was analysed using multiple-adjusted Cox proportional hazards models. Missing data were addressed through multiple imputation by chained equations. Results Higher disease activity parameters were found at baseline in very early axSpA. However, no significant differences were observed in treatment response or TNFi retention between very early and late axSpA (odds ratio for ASDAS < 2.1 response 0.99, 95% CI: 0.62-1.59 and hazard ratio for drug discontinuation 1.09, 95% CI: 0.87-1.37). Conclusions Based on this real-world observational data, no evidence was found to suggest a superior effectiveness of TNFi in patients with very early axSpA compared with those with late axSpA.