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Objectives. This study evaluated the cost effectiveness of adalimumab vs conventional therapy in patients with active ankylosing spondylitis (AS).

Methods. The analysis was based on pooled data from two Phase III studies of adalimumab in active AS. Patients with an inadequate response to >= 1 NSAID received adalimumab 40 mg every other week (n=246) or placebo (n=151) for 24 weeks. A microsimulation model was developed with patients being treated with adalimumab according to the International ASAS Consensus Statement and BSR guidelines. The pooled adalimumab data, as well as data from the Outcome Assessment in AS International Study (OASIS) database and the literature, were used to model patients’ BASDAI and BASFI scores and costs and health-related quality of life associated with various degrees of disease activity. Costs (in 2004 British) of AS, drug, administration, monitoring, hospitalization and AEs were calculated from the perspective of the UK NHS. Discounting was applied at 3.5% per year for costs and benefits as per the NICE reference case for economic evaluations. Uncertainty was addressed via sensitivity analyses.

Results. The incremental cost-effectiveness ratio (ICER) of adalimumab vs conventional therapy was estimated to improve with longer time horizons (48 weeks to 5 and 30 yrs). The central estimate was that, over 30 yrs, adalimumab therapy yielded 1.03 more quality-adjusted lifeyears (QALYs) per patient initiating therapy. Some AS treatment-related costs were estimated to be offset by adalimumab (at 10750 pound/ patient), leaving a total incremental cost (adalimumab vs conventional therapy) at 23857 pound per patient. The 30-yr ICER of adalimumab Vs conventional therapy was estimated at 23097 pound/QALY. Sensitivity analyses demonstrated robustness of results. When indirect costs were also included (analysis from societal perspective), ICER improved to 5093 pound/QALY.

Conclusions. This analysis indicates that adalimumab, when used according to UK treatment guidelines, is cost-effective vs conventional therapy for treating AS patients.