Tumor Necrosis Factor-α Inhibition in Ankylosing Spondylitis and Nonradiographic Axial Spondyloarthritis: Treatment Response, Drug Survival, and Patient Outcome

Objective. The purpose of this study was to (1) evaluate baseline characteristics of nonradiographic axial spondyloarthritis (nr-axSpA) and ankylosing spondylitis (AS) treated with tumor necrosis factor-alpha inhibitors (TNFi), (2) assess the response to first TNFi treatment, and (3) compare drug-survival duration and rates. Methods. Inclusion criteria were patients with axSpA who initiated first TNFi treatment between April 2001 and July 2014 and were followed up for at least 3 months. Efficacy criteria were an improvement of at least 2 points (on a 0-10 scale) or a 50% improvement in the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI). Baseline characteristics, responses at 12 months, and drug survival were compared between AS and nr-axSpA. Results. A total of 361 patients were included in the study (AS, n = 263 and nr-axSpA, n = 98). Patients with AS were more often men (65.02% vs 45.92%, p = 0.001) and had longer symptom duration (11.71 +/- 9.52 vs 7.34 +/- 9.30 yrs, p < 0.001). Median levels of acute-phase reactants (C-reactive protein and erythrocyte sedimentation rate) were significantly higher in patients with AS (p < 0.001 for both). Median BASDAI scores at first TNFi initiation were not higher in patients with nr-axSpA than in patients with AS (59, 49-70 vs 60, 50-70, p = 0.73). BASDAI 20 and BASDAI 50 response rates at 12 months were not statistically different between patients with AS and patients with nr-axSpA (74.58% vs 64.58%, p = 0.19 and 61.02% vs 50.00%, p = 0.19, respectively). No statistically significant difference in terms of survival was observed between patients with AS and nr-axSpA (p = 1.00). Conclusion. Treatment response and drug survival were similar in patients with AS and nr-axSpA after first TNFi initiation.