The cost-effectiveness of infliximab in the treatment of ankylosing spondylitis in Spain. Comparison of clinical trial and clinical practice data.

OBJECTIVE: To estimate the cost-effectiveness of treating ankylosing spondylitis (AS) with infliximab (Remicade) in Spain for up to 40 years.

METHODS: A previously published disease model was adapted to the Spanish setting using resource consumption from a cross-sectional burden of an illness study in 601 patients in Spain. Cost-effectiveness estimates were based on a placebo-controlled clinical trial as well as an open clinical study in Spain. In the model, patients with insufficient response to treatment at 12 weeks [Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) <4 or > or =50% reduction] discontinue treatment. The results are presented in 2005 euros, from societal and health-care payer perspectives.

RESULTS: In the societal perspective, infliximab treatment dominates standard treatment in both analyses. In the perspective of the health-care system, with the assumption that, over the long term, functional ability of patients on treatment would decline at half the natural rate, the cost per quality-adjusted life year (QALY) gained was estimated at EUR 22 519 (double-blind trial) and EUR 8866 (open study). Assuming that patients' function on treatment remains stable, the cost-effectiveness ratios are EUR 15 157 and EUR 5307, respectively. Under the most conservative assumption (no effect of treatment on progression), the ratios are EUR 31 721 and EUR 13 659, respectively. In addition, the results are sensitive to the time horizon and discontinuation rates.

CONCLUSIONS: Our results indicate that infliximab therapy for patients with active AS should be cost-effective both in the societal perspective (dominating) and in the perspective of the health-care system (ranges from EUR 5300 to EUR 32 000 per QALY) in Spain.