Population based cost utility study of interferon beta-1b in secondary progressive multiple sclerosis.

OBJECTIVE To evaluate the cost utility of interferon beta-1b in secondary progressive multiple sclerosis. DESIGN Population based cost utility model (healthcare perspective). Data on use of health services were obtained from case records and routine morbidity data and utility values from a EuroQol survey. Local and published costs were used. Effectiveness was modelled using data on relative risk reductions from a randomised trial of interferon beta-1b. SETTING Tayside region, 1993-5. SUBJECTS 132 ambulatory people with secondary progressive multiple sclerosis. MAIN OUTCOME MEASURES Cost per quality adjusted life year (QALY) gained. Rate of relapse and proportion becoming wheelchair dependent over three years. RESULTS The number needed to treat for 30 months to delay time to wheelchair dependence in one person by nine months was 18 (95% confidence interval 5 to 26). For every 18 people treated for 30 months, six relapses would be prevented, gaining 0.397 discounted QALYs. The cost per QALY gained was 1 024 667 pounds sterling (276 466 pounds sterling to 485 499 pound sterling). If treatment was restricted to patients attending neurology services, the number needed to treat was 14 (cost per QALY gained 833 pounds sterling 514 (161 358 pounds sterling to infinity)). The cost per QALY gained was not sensitive to changes in cost which took account of a societal perspective. CONCLUSIONS The cost per QALY gained from interferon beta is high because of the high drug cost and modest clinical effect. Resources could be used more efficiently elsewhere.