Predictors of treatment response and drug continuation in 842 patients with ankylosing spondylitis treated with anti-tumour necrosis factor: results from 8 years' surveillance in the Danish nationwide DANBIO registry

Objectives To use prospectively registered data from the Danish nationwide rheumatological database (DANBIO) to describe disease activity, clinical response, treatment duration and predictors of drug survival (ie, number of days individual patients maintained treatment) and clinical response among patients with ankylosing spondylitis (AS) receiving their first treatment series with a tumour necrosis factor a (TNF alpha) inhibitor. Methods 842 TNFa inhibitor naive patients with AS were identified in DANBIO. Clinical response, drug survival and predictors thereof were investigated. 'Clinical response' was defined as a 50% or 20 mm reduction in Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) within 6 months compared with baseline. Achievement of a BASDAI <40 mm within 6 months was used as a second response parameter. Results 603 patients (72%) were men, disease duration 5 (1-13) years (median (IQR), age 41 (32-50) years. 445 (53%) received infliximab, 247 (29%) adalimumab and 150 (18%) etanercept. Parameters at baseline/1-year follow-up were: C-reactive protein (CRP): 14 (7-27)/5 (2-10) mg/l, BASDAI 59 (44-72)/21 (8-39) mm, Bath Ankylosing Spondylitis Functional Index (BASFI) 50 (34-67)/24 (9-45) mm, Bath Ankylosing Spondylitis Metrology Index 40 (20-50)/20 (10-40) mm. Within 6 months, 407/644 patients (63%) achieved a clinical response. Median drug survival was 4.3 years. One-and 2-year survival rates were 74% and 63%, respectively. Baseline characteristics associated with longer drug survival were male gender, CRP > 14 mg/l and low visual analogue scale fatigue (Cox regression analysis). Age, TNFa inhibitor and methotrexate use were insignificant. CRP > 14 mg/l, lower BASFI and younger age at baseline was associated with clinical response and achievement of a BASDAI <40 mm (logistic regression analysis). Conclusion TNFa inhibitors provide a rapid and sustained decrease of disease activity among patients with AS in clinical practice. Factors associated with continued treatment, clinical response and achievement of a BASDAI <40 mm were identified.