Economic evaluation of Avonex (interferon beta-la) in patients following a single demyelinating event,” Multiple Sclerosis

Background: Interferon beta-1a (Avonex†) 30 mg, intramuscular (i.m.), once weekly is efficacious in delaying clinically definite multiple sclerosis (CDMS) following a single demyelinating event (SDE). This study determined the cost effectiveness of Avonex † compared to current treatment in delaying the onset of CDMS. Methods: A cost-effectiveness analysis (CEA) and cost-utility analysis (CUA) were performed from Ministry of Health (MoH) and societal perspectives. For CEA, the outcome of interest was time spent in the pre-CDMS state, termed monosymptomatic life years (MLY) gained. For CUA, the outcome was quality-adjusted monosymptomatic life years (QAMLY) gained. A Markov model was developed with transitional probabilities and utilities derived from the literature. Costs were reported in 2002 Canadian dollars. Costs and outcomes were discounted at 5%. The time horizon was 12 years for the CEA, and 15 years for the CUA. All uncertainties were tested via univariate and multivariate sensitivity analyses. Results: In the CEA, the incremental cost of Avonex † per MLY gained was $53 110 and $44 789 from MoH and societal perspectives, respectively. In the CUA, the incremental cost of Avonex † per QAMLY gained was $227 586 and $189 286 from MoH and societal perspectives, respectively. Both models were sensitive to the probability of progressing to CDMS and the analytical time horizon. The CUA was sensitive to the utilities value. Conclusion: Avonex † may be considered as a reasonably cost-effective approach to treatment of patients experiencing an SDE. In addition, the overall incremental cost-effectiveness profile of Avonex † improves if treatment is initiated in pre-CDMS rather than waiting until CDMS