Early Improvements in Disease Activity Indices Predict Long-Term Clinical Remission Suggested by the Treat-to-Target Strategy in Patients with Ankylosing Spondylitis Receiving TNF-α Inhibitor Treatment

This study evaluated the possibility of clinical remission suggested by the treat-to-target strategy and identified predictors of clinical remission in 139 patients with ankylosing spondylitis (AS) receiving tumor necrosis factor-α inhibitors (TNFi). Clinical remission criteria selected were AS Disease Activity Score Inactive Disease (ASDAS-ID) and Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) < 2 with normal C-reactive protein (CRP) levels (BASDAI-CRP). The longitudinal relationship between clinical parameters and clinical remission was assessed using generalized estimating equations (GEEs). Responders to ASDAS-ID and BASDAI-CRP increased from 32.4% to 68.9% and from 39.9% to 75.2% at months 3 and 33, respectively. Responders to ASDAS-ID and BASDAI-CRP almost overlapped. In the univariable GEE model, age and 3-month improvement in BASDAI, ASDAS-CRP, physician and patient global assessments, and spinal pain predicted clinical remission achievement, while the presence of syndesmophytes predicted ASDAS-CRP achievement, and normalized CRP at 3 months was associated with BASDAI-CRP achievement. Multivariable GEE analysis revealed age (odds ratio (OR): 0.67; 95% confidence interval (CI), 0.49–0.93) and 3-month BASDAI improvement (OR: 1.70; CI, 1.19–2.41) as independent predictors of ASDAS-ID achievement and age (OR: 0.69; CI, 0.54–0.89), 3-month BASDAI improvement (OR: 2.00; CI, 1.45–2.76), and normalized CRP at 3 months (OR: 3.72; CI, 1.39–9.95) as independent predictors of BASDAI-CRP achievement