Cost-Effectiveness of Clopidogrel plus Aspirin versus Aspirin Alone for Secondary Prevention of Cardiovascular Events: Results from the CHARISMA Trial

Abstract

To determine the incremental cost-effectiveness of clopidogrel plus aspirin (C + A) compared with aspirin (A) alone during the Clopidogrel for High Atherothrombotic Risk and Ischemic Stabilization, Management and Avoidance (CHARISMA) trial from a US payer perspective. Although the CHARISMA trial did not find a benefit of adding clopidogrel to aspirin in its overall study cohort, a benefit was suggested in a prespecified subgroup of patients with established cardiovascular (CV) disease. The cost-effectiveness of dual antiplatelet therapy in this population is unknown. Medical resource utilization was assessed prospectively, and costs for hospitalizations, physician services, outpatient care, and medications were assigned using 2007 US dollars. Life expectancy was estimated contingent on fatal and nonfatal CV events using statistical models of long-term survival from the Saskatchewan Health database. C + A was associated with a 12.5% relative reduction in CV death, myocardial infarction, or stroke compared with A alone (6.9% vs. 7.9%, P = 0.048) over a median 28 months of follow-up. Severe or moderate bleeding events were higher in patients receiving C + A versus A alone (3.6% vs. 2.5%, P < 0.001). Mean cost/patient was $2607 higher for C + A, while projected life expectancy increased by an average of 0.072 years due to fewer in-trial events. The resulting incremental cost-effectiveness ratio (ICER) for C + A was $36,343/year of life gained. Findings were insensitive to discount rate, life expectancy projections, post-event costs, and indirect costs from lost productivity; the ICER was most sensitive to the cost of clopidogrel. Bootstrap analysis demonstrated that the ICER for C + A remained <$50,000/life-year gained in 70.6% of bootstrap replicates and <$100,000/life-year gained in 87.4%. Among patients with established CV disease, adding clopidogrel to aspirin appears to increase life expectancy modestly at a cost generally considered acceptable within the US health-care system.