A cost-effectiveness analysis of combination antiplatelet therapy for high-risk acute coronary syndromes: clopidogrel plus aspirin versus aspirin alone.

BACKGROUND: Although clopidogrel plus aspirin is more effective than aspirin alone in preventing subsequent vascular events in patients with unstable angina, the cost-effectiveness of this combination has yet to be examined in this high-risk population.

OBJECTIVE: To determine the cost-effectiveness of clopidogrel plus aspirin compared with aspirin alone.

DESIGN: Cost-utility analysis.

DATA SOURCES: Published literature.

TARGET POPULATION: Patients with unstable angina and electrocardiographic changes or non-Q-wave myocardial infarction. time horizon: Lifetime.

PERSPECTIVE: Societal.

INTERVENTIONS: Combination therapy with clopidogrel, 75 mg/d, plus aspirin, 325 mg/d, for 1 year, followed by aspirin monotherapy, was compared with lifelong aspirin therapy, 325 mg/d.

OUTCOME MEASURES: Lifetime costs, life expectancy in quality-adjusted life-years (QALYs), and the incremental cost-effectiveness ratio.

RESULTS OF BASE-CASE ANALYSIS: Patients treated with aspirin alone lived 9.51 QALYs after their initial event and incurred expenses of 127,700 dollars; the addition of clopidogrel increased life expectancy to 9.61 QALYs and costs to 129,300 dollars. The incremental cost-effectiveness ratio for clopidogrel plus aspirin compared with aspirin alone was 15,400 dollars per QALY.

RESULTS OF SENSITIVITY ANALYSES: The analysis of 1 year of therapy was robust to all sensitivity analyses. In the probabilistic sensitivity analysis, fewer than 3% of simulations resulted in cost-effectiveness ratios over 50,000 dollars per QALY. The cost-effectiveness of longer combination therapy depends critically on the balance of thrombotic event rates, durable efficacy, and the increased bleeding rate in patients taking clopidogrel.

LIMITATIONS: This analysis may not apply to patients with severe heart failure, those undergoing long-term anticoagulant therapy, those recently managed with revascularization, or those undergoing short-term treatment with glycoprotein IIb/IIIa inhibitors.

CONCLUSIONS: In patients with high-risk acute coronary syndromes, 1 year of therapy with clopidogrel plus aspirin results in greater life expectancy than aspirin alone, at a cost within the traditional limits of cost-effectiveness. The durable efficacy of clopidogrel relative to the risk for hemorrhage should be further explored before more protracted therapy can be recommended.