Cost-effectiveness of warfarin and aspirin for prophylaxis of stroke in patients with nonvalvular atrial fibrillation.

OBJECTIVE

To examine the cost-effectiveness of prescribing warfarin sodium in patients who have nonvalvular atrial fibrillation (NVAF) with or without additional stroke risk factors (a prior stroke or transient ischemic attack, diabetes, hypertension, or heart disease).

DESIGN

Decision and cost-effectiveness analyses. The probabilities for stroke, hemorrhage, and death were obtained from published randomized controlled trials. The quality-of-life estimates were obtained by interviewing 74 patients with atrial fibrillation. Costs were estimated from literature review, phone survey, and Medicare reimbursement.

PATIENTS

In the base case, the patients were 65 years of age and good candidates for warfarin therapy.

INTERVENTIONS

Treatment with warfarin, aspirin, or no therapy in the decision analytic model.

MAIN OUTCOME MEASURES

Quality-adjusted survival and marginal cost-effectiveness of warfarin as compared with aspirin or no therapy.

RESULTS

For patients with NVAF and additional risk factors for stroke, warfarin therapy led to a greater quality-adjusted survival and to cost savings. For patients with NVAF and one additional risk factor, warfarin therapy cost $8000 per quality-adjusted life-year saved. For 65-year-old patients with NVAF alone, warfarin cost about $370,000 per quality-adjusted life-year saved, as compared with aspirin therapy. However, for 75-year-old patients with NVAF alone, prescribing warfarin cost $110,000 per quality-adjusted life-year saved. For patients who were not prescribed warfarin, aspirin was preferred to no therapy on the basis of both quality-adjusted survival and cost in all patients, regardless of the number of risk factors present.

CONCLUSIONS

Treatment with warfarin is cost-effective in patients with NVAF and one or more additional risk factors for stroke. In 65-year-old patients with NVAF but no other risk factors for stroke, prescribing warfarin instead of aspirin would affect quality-adjusted survival minimally but increase costs significantly.