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The Cost-Effectiveness of Infliximab (Remicade®) in the Treatment of Ankylosing Spondylitis in Canada GISELA KOBELT, PATRIK ANDLIN-SOBOCKI, and WALTER P. MAKSYMOWYCH ABSTRACT. Methods. A previously published disease model based on functional capacity and disease activity was adapted to the Canadian setting. Current resource consumption from a cross-sectional bottom-up burden-of-illness study in 545 patients at different levels of severity of AS in 4 Canadian provinces was incorporated into the model. Cost-effectiveness estimates were based on a 3-month placebo-controlled clinical trial with 2-year open extension as well as a 4-year followup study of clinical practice in Canada. In the cost-effectiveness model, patients with insufficient response to treatment at 12 weeks (≥ 50% reduction in Bath Ankylosing Spondylitis Disease Activity Index) discontinue treatment. In view of the long disease duration, simulations over a 30-year timeframe were performed, incorporating disease progression from cohort studies and assumptions about treatment continuation beyond the clinical trial from the trial extension period. Results are presented in Canadian dollars, from the societal and healthcare payer perspectives, with both costs and effects discounted at 5%. Results. Over a 30-year timeframe, with the assumption that patients' disease would remain stable while on treatment, the cost per quality-adjusted life-year (QALY) gained in the societal perspective is $37,491, using the treatment regimen in the clinical trial (5 mg/kg every 6 weeks). Using the dosing regimen of the Canadian study (75% at 3 mg/kg every 8 weeks, 15% at 3 mg/kg every 6 weeks, and 10% at 5 mg/kg every 8 weeks) the cost per QALY is $10,264. Assuming that patients on treatment progress at half the rate of untreated patients, the cost-effectiveness ratios are $45,121 and $13,883, respectively, while the most conservative assumption that progression is the same in both arms, the ratios are $54,137 and $18,712, respectively. The results are sensitive to the dosing regimen adopted, the discontinuation rate, and assumptions concerning disease progression while on treatment. Conclusion. Our results indicate that infliximab therapy for patients with active AS would be cost-effective (ranges $10,264–$54,137 per QALY) in a Canadian setting. (J Rheumatol 2006;33:732–40)
Key Indexing Terms: COST EFFECTIVENESS
From the European Health Economics SAS, Mulhouse, France, and Stockholm, Sweden; the Karolinska Institute, Stockholm; and Division of Rheumatology, University of Alberta, Edmonton, Alberta, Canada. Supported by an unrestricted grant from Schering Plough Canada. G. Kobelt, PhD, European Health Economics SAS and Karolinska Institute; P. Andlin-Sobocki, MS, European Health Economics SAS; W.P. Maksymowych, MD, Division of Rheumatology, University of Alberta. Address reprint requests to G. Kobelt, European Health Economics SAS, 492 chemin des Laurens, 06530 Spéracèdes, France. E-mail: Gisela.Kobelt@he-europe.com Accepted for publication November 25, 2005.
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