Objective: To estimate the cost-effectiveness (CE) of interferon beta-1b (IFNβ-1b) in slowing disability progression in persons with relapsing-remitting multiple sclerosis (RRMS).

Methods: Treatment program costs and health outcomes are modeled for cohorts of 1,000 females and 1,000 males followed 40 years from onset. Fifteen scenarios model MS natural history progression, treatment efficacy, direct treatment costs, and MS healthcare costs. A single randomized placebo-controlled trial of IFNβ-1b found reduced disease activity by MRI, reduced frequency and severity of exacerbations, and a tendency toward slower disability progression.

Disability years avoided are modeled as the primary health outcome analyzed. A ministry of health (MOH) perspective is adopted, using Nova Scotia population-based data. Annual IFNβ-1b direct treatment costs (Can $16,685) are high relative to both MOH healthcare costs per person with MS (Can $2,000) and estimated MOH costs avoided.

Results: Given “reference case” assumptions for women with RRMS, treatment reduces lifetime disability years by 10%. Cost per disability year avoided before discounting is Can $189,230 (US $124,892), and Can $274,842 (US $181,395) after discounting at 5%. Estimates for alternative scenarios vary greatly, leaving main findings unchanged.

Conclusions: Using the Expanded Disability Status Scale, cost per disability year avoided due to interferon beta-1b treatment in RRMS is quite high. Comparable CE estimates, using MS-specific or generic health-related quality-of-life outcome measures, are even higher. Further research is required to better measure treatment effects, modification of MS natural history, and net societal costs of IFNβ-1b in RRMS.