Efficiency of adalimumab, etanercept and infliximab in ankylosing spondylitis in clinical practice

Background Information on the use of ankylosing spondylitis (AS) therapies in clinical practice is a key factor in decision making, as more efficient treatments may involve substantial savings while maintaining the clinical benefits for the patient. Objective To assess the mean annual doses and associated costs of the three main anti-tumour necrosis factor agents used in Spanish daily clinical practice in ankylosing spondylitis patients and to correlate these costs with disease activity. Setting This retrospective, observational study included adult ankylosing spondylitis patients over a 4-year period that had been treated for at least 6 months with adalimumab, etanercept or infliximab at two University Hospitals in Spain. Methods Disease activity was estimated with Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) scores at the start of anti-tumour necrosis factor (anti-TNF) therapy and in the last visit or whenever the drug was switched. Mean costs were estimated for a 52-week horizon from the delivered doses registered by pharmacy records. Outcomes were the doses and costs of anti TNFs administered to each patient, and the BASDAI score. Results A total of 119 patients (137 cases) were included (28 cases treated with adalimumab, 48 cases with etanercept and 61 with infliximab). Mean doses of adalimumab and etanercept were 92.8 and 88.8 % of the initially prescribed doses, respectively, while the mean dose of infliximab administered was 102 %. There were no statistical differences among treatments in terms of clinical effectiveness. Associated mean patient-year costs were significantly higher in the infliximab group (€14,235), compared to the other treatments [adalimumab €11,934; etanercept €10,516; (P < 0.05)]. Conclusion In certain ankylosing spondylitis patients, doses and associated costs of biological therapies can be reduced while controlling disease activity. Mean doses used in our clinical practice vary from the recommended doses and are significantly lower for adalimumab and etanercept than for infliximab. These differences impact directly on associated patient-year costs, and, thus, on treatment efficiency.