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Cost-Effectiveness of Clopidogrel plus Aspirin versus Aspirin Alone
Mark D. Schleinitz, MD, MS, and
Paul A. Heidenreich, MD, MS
20 September 2005 | Volume 143 Issue 6 | Pages 464-465
IN RESPONSE:
Dr. Rothberg suggests that our analysis would have been stronger if we had used outcome-specific estimates of the efficacy of clopidogrel when added to aspirin. We agree in theory and have used this approach in an analysis of clopidogrel monotherapy (1). The CURE trial (2), however, did not report the numbers of each type of event that made up the composite outcomes. The cardiovascular death rate cited by Rothberg, for example, is itself a composite of deaths due to stroke, myocardial infarction, and other cardiovascular causes. We felt that the potential to introduce bias by estimating event rates for aspirin monotherapy as well as combination therapy and using these calculations to approximate outcome-specific efficacy was too great to justify this method.
Dr. Eriksson emphasizes our point that balancing protection from thrombotic events with the risk for hemorrhage is critical in determining the benefit of adding clopidogrel to aspirin, and thereby its cost-effectiveness. Assuming constant relative efficacy of combination therapy, we found that the diminishing absolute benefit in thrombotic event rates is negated by the constant risk for hemorrhage after 5 years.
Cost may help specify the "ideal" duration of therapy in 1 of 2 ways: at the average individual level, as reflected by the incremental cost-effectiveness ratio, or at the societal budgetary level, a function of both the incremental cost-effectiveness ratio and the size of the affected population. Variation in both societal preference and available resources means that this "ideal" duration may differ among countries.
Eriksson also notes that in a post hoc evaluation, the efficacy estimate of adding clopidogrel to aspirin varied with the dose of aspirin (3). Aspirin dose was determined at the physician's discretion. We have shown that efficacy estimates of antiplatelet therapies derived from nonrandomized studies may be statistically distinct from results of randomized comparisons (4), and we agree that a randomized comparison is warranted to clarify the optimal dose of aspirin for combination therapy.
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Author and Article Information
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From Brown University, Providence, RI 02903, and VA Palo Alto Healthcare System, Palo Alto, CA 94304.
Potential Financial Conflicts of Interest: None disclosed.
1. Schleinitz MD, Weiss JP, Owens DK. Clopidogrel versus aspirin for secondary prophylaxis of vascular events: a cost-effectiveness analysis. Am J Med. 2004;116:797-806. [PMID: 15178495].[Medline]
2. Yusuf S, Zhao F, Mehta SR, Chrolavicius S, Tognoni G, Fox KK, et al. Effects of clopidogrel in addition to aspirin in patients with acute coronary syndromes without ST-segment elevation. N Engl J Med. 2001;345:494-502. [PMID: 11519503].[Abstract/Free Full Text]
3. Peters RJ, Mehta SR, Fox KA, Zhao F, Lewis BS, Kopecky SL, et al. Effects of aspirin dose when used alone or in combination with clopidogrel in patients with acute coronary syndromes: observations from the Clopidogrel in Unstable angina to prevent Recurrent Events (CURE) study. Circulation. 2003;108:1682-7. [PMID: 14504182].[Abstract/Free Full Text]
4. Schleinitz MD, Olkin I, Heidenreich PA. Cilostazol, clopidogrel or ticlopidine to prevent sub-acute stent thrombosis: a meta-analysis of randomized trials. Am Heart J. 2004;148:990-7. [PMID: 15632883].[Medline]
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Articles
A Cost-Effectiveness Analysis of Combination Antiplatelet Therapy for High-Risk Acute Coronary Syndromes: Clopidogrel plus Aspirin versus Aspirin Alone
Mark D. Schleinitz AND Paul A. Heidenreich
- Annals 2005 142: 251-259.
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