Clinical Question: Is dabigatran cost-effective as compared with warfarin for patients with atrial fibrillation?

Bottom Line: Dabigatran is only cost-effective for patients who have poorly controlled INR, or who are at high risk of bleeding and/or stroke. It is worth pulling the article to review Figure 3, which can be used to guide point-of-care decision-making. (Level of Evidence: 2b)

Reference: Shah SV, Gage BF. Cost-effectiveness of dabigatran for stroke prophylaxis in atrial fibrillation. Circulation 2011;123(22):2562-2570.

Study Design: Cost-effectiveness analysis

Funding Source: Foundation

Setting: Population-based

Synopsis: Dabigatran, an oral direct thrombin inhibitor, is an expensive but more convenient alternative to warfarin, since it does not require monitoring. It is argued that although the direct drug cost of dabigatran is much higher than that of warfarin, the cost is offset by not needing visits for monitoring. This cost-effectiveness analysis, funded by the American Heart Association, attempts to determine whether this is true. The authors compared 6 strategies: no treatment, aspirin once daily, aspirin plus clopidogrel, warfarin, dabigatran 110 mg twice daily, and dabigatran 150 mg twice daily. The base case was the typical 70-year-old patient with atrial fibrillation, a moderate risk of stroke, and no contraindication to anticoagulation. The authors also varied the risk of stroke (based on the CHADS2 score) and risk of major bleeding (based on the HEMORR2HAGES score) to see the impact of changing risk on the optimal strategy. The authors used reasonable estimates of benefits, harms, and costs in their model, and they performed sensitivity analyses to study the effect of varying the base estimates. For example, the risk of stroke was varied from 0.8/100 to 13.7/100 person-years; major bleeding from 1.9/100 to 10.4/100 person-years; patient age from 60 years to 80 years; and time in the therapeutic INR range from less than 57% to more than 72%. In the Markov model, patients moved from one health state to another, or stayed in the same health state, each month. This was repeated for up to 20 years, with the costs and outcomes determined for each of the 6 strategies. For the base case, warfarin cost an additional $12,000 per quality adjusted life year (QALY) compared with aspirin. (A therapy is generally considered cost-effective if it costs less than $50,000/QALY). Dabigatran 150 mg cost $86,000/QALY using the base case assumption, while dabigatran 110 mg cost $150,000/QALY. Dual therapy with aspirin and clopidogrel resulted in fewer QALYs for higher cost, so it wasn't even in the running. For the base case, dabigatran was cost-effective for patients at high risk of stroke (CHADS2 score = 3 or higher) and those ar moderate risk of stroke but at high risk of bleeding. The sensitivity analysis also showed that for patients who had less than 57% time in the therapeutic range, dabigatran was the preferred option if the CHADS2 score was 2 or higher, but if patients spent more than 72% of time in range, dabigatran was never the preferred option. For patients with a CHADS2 score of 0 or 1, treatment with aspirin or no treatment was often the preferred strategy.