Cost-effectiveness of apixaban compared with aspirin for stroke prevention in atrial fibrillation among patients unsuitable for warfarin.

BACKGROUND: Compared with aspirin, apixaban reduces stroke risk in atrial fibrillation (AF) patients unsuitable for warfarin by 63% but does not increase major bleeding. We sought to determine the cost-effectiveness of apixaban versus aspirin. METHODS AND RESULTS: Using the Apixaban versus Acetylsalicylic Acid to Prevent Stroke in Atrial Fibrillation Patients Who Have Failed or Are Unsuitable for Vitamin-K Antagonist Treatment (AVERROES) trial and other studies, we constructed a Markov model to evaluate the costs (2011US$), quality-adjusted life-years (QALYs), and incremental cost-effectiveness of apixaban versus aspirin from the Medicare perspective. Our base-case assumed a 70-year-old AF patient cohort with a CHADS(2) score=2 and a lower-risk of bleeding. We used a 1-month cycle-length and ran separate base-case analyses assuming a trial-length (1-year) and a longer-term (10-year) follow-up. Total costs/patient were $3454 and $1805 for apixaban and aspirin in the trial-length and $44 232 and $50 066 in the 10-year model. Corresponding QALYs were 0.96 and 0.96 in the trial-length and 6.87 and 6.51 in the 10-year model, making apixaban inferior in the first model but dominant in the latter. Conclusions were sensitive to baseline stroke rate in both models, and the monthly cost of major stroke, relative risk of stroke, and prior vitamin-K antagonist use in the life-time model. Probabilistic sensitivity analysis suggested apixaban would only be a cost-effective alternative (<$50 000/QALY) to aspirin 11% of the time in the trial-length model, but cost-effective or dominant 96.7% and 87.5% of iterations in the 10-year model. CONCLUSIONS: In our trial-length model, apixaban was more costly and no more effective than aspirin; however, as follow-up was extended, apixaban became cost-effective and eventually dominant.

Cost-effectiveness of clopidogrel plus aspirin for stroke prevention in patients with atrial fibrillation in whom warfarin is unsuitable.

Guidelines for atrial fibrillation (AF) recommend clopidogrel plus aspirin as an alternative stroke prevention strategy in patients in whom warfarin is unsuitable. A Markov model was conducted from a Medicare prospective using data from the Atrial Fibrillation Clopidogrel Trial with Irbesartan for Prevention of Vascular Events-A (ACTIVE-A) trial and other published studies. Base-case analysis evaluated patients 65 years old with AF, a CHADS(2) (congestive heart failure, 1 point; hypertension defined as blood pressure consistently >140/90 mm Hg or antihypertension medication, 1 point; age ≥75 years, 1 point; diabetes mellitus, 1 point; previous stroke or transient ishemic attack, 2 points) score of 2, and a lower risk for major bleeding. Patients received clopidogrel 75 mg/day plus aspirin or aspirin alone. Patients were followed for up to 35 years. Outcomes included quality-adjusted life-years (QALYs), costs (in 2011 American dollars), and incremental cost-effectiveness ratios. Quality-adjusted life expectancy and costs were 9.37 QALYs and $88,751 with clopidogrel plus aspirin and 9.01 QALYs and $79,057 with aspirin alone. Incremental cost-effectiveness ratio for clopidogrel plus aspirin was $26,928/QALY. With 1-way sensitivity analysis using a willingness-to-pay threshold of $50,000/QALY, clopidogrel plus aspirin was no longer cost effective when the CHADS(2) score was ≤1, major bleeding risk with aspirin was ≥2.50%/patient-year, the relative risk decrease for ischemic stroke with clopidogrel plus aspirin versus aspirin alone was <25%, and the utility of being healthy with AF on combination therapy decreased to 0.95. Monte Carlo simulation demonstrated that clopidogrel plus aspirin was cost effective in 55% and 73% of 10,000 iterations assuming willingness-to-pay thresholds of $50,000 and $100,000/QALY. In conclusion, clopidogrel plus aspirin appears cost-effective compared to aspirin alone for stroke prevention in patients with AF with a CHADS(2) of ≥2 and a lower risk of bleeding.