RESUMO
The cost-effectiveness of hepatitis C virus (HCV) anti-viral therapy for injecting drug users (IDUs) on methadone maintenance is important because the majority have chronic infections that remain untreated. Cost-effectiveness analysis examines the costs of treatment compared with the benefits, which in this study are defined as savings in life. The cost-effectiveness of treatment for HCV infection is investigated for Mäori and non-Mäori IDUs on methadone maintenance therapy (MMT) in New Zealand. Markov models are used to model cohorts of IDUs, changes in their health states and the effects of MMT and anti-viral therapy on morbidity and mortality. Comparisons were made between conventional combination therapy (COT) and combination therapy with pegylated interferon. Sensitivity analysis is used to model cost-effectiveness of treatment under varying assumptions of progression of liver disease and compliance with treatment. The cost-effectiveness of MMT alone was estimated at 25397 dollars per life year saved (LYS) for non-Mäori men and 25035 dollars for non-Mäori women IDUs (costs and benefits discounted at 3%). The incremental effects of providing COT to all eligible patients were to save extra years of life, as well as to involve additional costs of anti-viral therapy. Analysis of both the incremental costs and benefits showed that a policy of providing COT to all patients meeting treatment criteria would have similar cost-effectiveness to MMT alone. Costs per LYS were estimated to be lower for Mäori for both men and women, reflecting ethnic differences in mortality. Cost-effectiveness was found to improve if the average age of stabilizing on MMT could be lowered by 5 years from the current average age of 31 years to age 26. Cost-effectiveness of the new treatment with pegylated interferon and ribavirin was found to be similar to that of COT because the increased LYS were offset by expected higher costs of the new pharmaceuticals. Sensitivity analysis showed that anti-viral treatment remained cost-effective under varying assumptions of the rate of disease progression and compliance with treatment.
