Efficacy and drug survival of anti-tumour necrosis factor-alpha therapies in patients with non-radiographic axial spondyloarthritis: an observational cohort study from Southern Sweden

Objectives: To evaluate the efficacy and drug survival of anti-tumour necrosis factor (anti-TNF) therapy in non-radiographic axial spondyloarthritis (nr-axSpA) patients treated in clinical practice in Southern Sweden. Method: In this cohort study we prospectively included 112 patients with nr-axSpA and high disease activity as well as inadequate response or intolerance to non-steroidal anti-inflammatory drugs (NSAIDs) receiving their first course of anti-TNF therapy. Patients fulfilling modified New York criteria for ankylosing spondylitis (AS) were excluded. The Assessment of SpondyloArthritis International Society (ASAS) criteria for axial SpA were fulfilled by 77% (n = 86) of the included patients. Results: At baseline, the median age of the cohort was 38 years, 59% were males, 79% of the patients had imaging suggestive of sacroiliitis (primarily inflammation on magnetic resonance imaging, MRI), 71% were HLA-B27 positive, and the median disease duration was 6 years and 10 months. At 6 months of follow-up, the median Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) decreased from 5.6 to 3.2 (p = 0.002), the Bath Ankylosing Spondylitis Functional Index (BASFI) decreased from 3.9 to 1.8 (p = 0.005), and C-reactive protein (CRP) level decreased from 4.4 to 1.7 mg/L (p = 0.001). After 1 year of treatment the Kaplan-Meier estimated drug survival was 76%, and at 2 years of follow-up this value decreased to 65%. Patients with inflammatory MRI findings at baseline had significantly better drug survival [hazard ratio (HR) 0.24, 95% confidence interval (CI) 0.10-0.55, p = 0.001]. Male sex was also associated with higher drug survival (HR 0.45, 95% CI 0.24-0.85, p = 0.011). CRP level at baseline was not associated with drug survival. Conclusions: Anti-TNF treatment of patients with nr-axSpA in clinical practice resulted in reduced BASDAI and BASFI scores and good drug survival. The results from this study suggest that male gender and positive imaging at baseline are associated with a favourable treatment course.