ECONOMIC EVALUATION OF ANTIPLATELETS IN THE SECONDARY PREVENTION OF VASCULAR EVENTS IN STROKE PATIENTS

Purpose:    To assess the comparative cost-effectiveness of antiplatelets in the secondary prevention of recurrent stroke (fatal or non-fatal), in patients who have had a stroke.

Method:    A Markov model for cost-utility analysis was constructed using Microsoft Office Excel 2003. The comparators were clopidogrel, acetylsalicylic acid (ASA), ASA plus clopidogrel, dipyridamole, combination of fixed-dose ASA and extended-release dipyridamole (ASA-ERDP), and ticlopidine. In the base-case analysis it was assumed starting age was 60 years, and that the treatment duration with the interventions was two years followed by ASA treatment for the remaining years. The perspective was that of a provincial ministry of health, and the time horizon was lifetime. Clinical inputs were based on a mixed treatment comparison meta-analysis done in parallel with the economic evaluation. One-way sensitivity analysis was done on a variety of alternative parameters and assumptions. A probabilistic sensitivity analysis was conducted using Monte Carlo simulation and cost-effectiveness acceptability curves were derived. The model allowed analysis of the effect of changing both the starting age of treatment, and treatment duration.

Result:    At a starting age of 60 years at the time of initial stroke, lifetime treatment using ASA dominated the other treatment options because it had lower costs and higher expected QALYs. As the mean age at the start of treatment increased, the sequential incremental cost-effectiveness ratio (ICER) results for ASA-ERDP and clopidogrel were respectively $48,904 and $1,857,374 at age 70; $41,004 and $845,141 at age 75; and $33,046 and $214,901 at age 85. When ASA was removed as an option, the ICER for ASA-ERDP versus ticlopidine (least cost option after ASA) was $26,142 per QALY gained.

Conclusion:    For patients with mean age 60 years at the time of their initial stroke, at a willingness-to-pay threshold of $50,000 per QALY ASA is the most cost-effective treatment option for the secondary prevention of recurrent stroke. ASA-ERDP may be a cost-effective alternative for patients in this age group who do not tolerate ASA. ASA-ERDP was found to be the most cost-effective treatment option for patients 70 years of age or older at the time of their initial stroke.