Presence of peripheral arthritis and male sex predicting continuation of anti–tumor necrosis factor therapy in ankylosing spondylitis: An observational prospective cohort study from the South Swedish arthritis treatment group register




To examine clinical characteristics as possible predictors of long-term treatment continuation with adalimumab, etanercept, and infliximab in ankylosing spondylitis (AS) patients who had never taken biologics treated in clinical practice.


Patients in southern Sweden with active AS starting biologic therapy for the first time between October 1999 and December 2008 (n = 243, 75% men) were included in a structured clinical followup over 2 years. Patients with clinical spondylitis had not responded to at least 2 nonsteroidal antiinflammatory drugs, whereas patients who also had peripheral arthritis (n = 121) had additionally failed at least 1 conventional disease-modifying antirheumatic drug (DMARD) treatment course. The mean ± SD age at inclusion was 43 ± 12 years, with a mean ± SD disease duration prior to treatment of 16 ± 12 years.


The 2-year drug continuation rate was 74%. Male sex (hazard ratio [HR] of premature discontinuation 0.36 [95% confidence interval (95% CI) 0.19–0.68]) and the presence of peripheral arthritis (HR 0.49 [95% CI 0.27–0.88]) were found to be significant predictors of better drug survival. Furthermore, a trend was seen for more favorable drug continuation on treatment with etanercept as compared with infliximab (HR 0.50 [95% CI 0.25–1.04], P = 0.062), whereas no differences were found comparing the 3 anti–tumor necrosis factor agents in other ways. Higher baseline C-reactive protein level (HR 0.99 [95% CI 0.97–1.00], P = 0.12) and concomitant treatment with nonbiologic DMARDs (HR 0.61 [95% CI 0.34–1.10], P = 0.10) also showed trends to entail better drug adherence.


AS patients in this study have an excellent 2-year drug survival rate of 74%. Significant predictors for treatment continuation in this study were male sex and the presence of peripheral arthritis.