Abstract 8301: Clopidogrel Plus Aspirin is Cost-Effective for Stroke Prevention in Patients with Atrial Fibrillation in Whom Warfarin is Unsuitable

Abstract

Introduction: Updated guidelines for atrial fibrillation (AF) now recommend clopidogrel plus aspirin as an alternative stroke prevention strategy in patients whom warfarin is unsuitable. Objective: To evaluate the cost-effectiveness of clopidogrel plus aspirin compared to aspirin alone for stroke prevention in patients with nonvalvular AF (NVAF). Methods: A Markov model was conducted from the societal prospective using data from the Atrial Fibrillation Clopidogrel Trial with Irbesartan for Prevention of Vascular Events (ACTIVE)-A trial and other published studies of anticoagulation. Drug cost was estimated using the average wholesale price and the cost of complications and adverse events was based on values from the Healthcare Cost and Utilization Project and CMS reimbursement rates. The base-case analysis evaluated patients aged 65 years with NVAF, a CHADS 2 score of 2 and a low risk for major bleeding. Patients received clopidogrel 75 mg daily plus aspirin (recommended dose of aspirin: 75-100 mg daily) or aspirin alone. Patients were followed for up to 35 years. Outcomes included quality-adjusted life-years (QALYs), costs, and incremental cost-effectiveness ratios (ICERs). Costs were inflated to 2011US$ using the Consumer Price Index for Medical Care. Future costs and QALYs were discounted at a rate of 3% annually. Results: Quality-adjusted life expectancy and therapy-related costs were 9.37 QALYs and $88,751 with clopidogrel plus aspirin and 9.01 QALYs and $79,057 with aspirin alone. The ICER for clopidogrel plus aspirin was $26,928/QALY. Upon one-way sensitivity analysis, using a willingness-to-pay (WTP) threshold of $50,000/QALY, clopidogrel plus aspirin was no longer cost-effective when CHADS 2 score was ≤1, major bleeding risk with aspirin was ≥2.50%/patient-year and the relative risk reduction for ischemic stroke with clopidogrel plus aspirin vs. aspirin alone was <25%. Monte Carlo simulation demonstrated that clopidogrel plus aspirin was cost-effective in 55% and 73% of 10,000 iterations, assuming WTP thresholds of $50,000 and $100,000/QALY. Conclusion: Clopidogrel plus aspirin appears cost-effective compared to aspirin alone for stroke prevention in patients with NVAF who have at least a CHADS 2 of 2 and a low risk of bleeding.