Clopidogrel versus aspirin in patients with atherothrombosis: a CAPRIE-based cost-effectiveness model for Greece

Atherothrombosis represents a leading cause of morbidity and mortality worldwide. Given the prominent role of platelet aggregation in atherothrombosis, antiplatelet therapy forms the cornerstone of treatment, with proven efficacy in the secondary prevention of atherothrombotic events. Although clopidogrel seems to be superior to aspirin in terms of risk reduction for an atherothrombotic event, whether this clinical advantage is cost effective in Greece is unknown.

The aim of this study was to conduct a cost-effectiveness analysis comparing clopidogrel with aspirin in the secondary prevention of atherothrombotic events in patients with peripheral artery disease, a recent stroke or a recent myocardial infarction, from the third-party-payer perspective in Greece.

A Markov model with a 6-month cycle length was developed. Transition probabilities used in the model were obtained from the event rates reported in the CAPRIE trial. The effect of clopidogrel was applied only during the first 2 years of the model. Utility data were used to estimate quality-adjusted life-years (QALYs). Costs (for the year 2012) assigned to each health state included antiplatelet treatment cost, cost for the management of adverse events related to antiplatelet therapy and the direct healthcare cost of patients (i.e. concomitant medication, hospitalization, outpatient visits, rehabilitation, laboratory and imaging diagnostic examinations as well as interventions) in the acute and follow-up phase, separately. The incremental cost-effectiveness ratio (ICER) was calculated for life-years (LYs) and QALYs, separately. A probabilistic sensitivity analysis was conducted in order to evaluate the impact of the variation that characterizes the majority of model parameters to the cost-effectiveness results.

The Markov analysis revealed that the discounted survival was 11.83 (95% CI 11.40, 12.22) years and 12.17 (95% CI 11.75, 12.55) years in the aspirin and clopidogrel treatment groups, respectively, a difference of 0.34 (95% CI 0.09, 0.618) LYs. The corresponding discounted QALYs were 8.63 (95% CI 8.34, 8.90) and 8.84 (95% CI 8.54, 9.10), respectively, a difference of 0.21 (95% CI 0.05, 0.37) QALYs. The cumulated lifetime costs per patient were €20 678 (95% CI 19 675, 21 724) and €21 688 (95% CI 20 649, 22 773), for aspirin and clopidogrel treatment arm, respectively. The ICER for clopidogrel was calculated to be €4038 (95% CI 2743, 7837) for each LY saved and €5518 (95% CI 3358, 12 921) for each QALY saved.

The analysis indicates that clopidogrel is cost effective for the secondary prevention of atherothrombotic events in the Greek setting. These findings are in line with those reported in other European countries.