Apixaban versus Warfarin in Atrial Fibrillation

To the Editor: In the article by Granger et al. describing the results of the Apixaban for Reduction in Stroke and Other Thromboembolic Events in Atrial Fibrillation (ARISTOTLE) study (Sept. 15 issue),¹ it was disappointing that patients with atrial fibrillation who were treated with warfarin had an international normalized ratio (INR) within the therapeutic range only 62% of the time. This percentage is particularly low considering that such a range can be achieved 76% of the time among patients receiving warfarin in Europe.² Therefore, the ARISTOTLE study was effectively comparing apixaban therapy with poorly controlled warfarin therapy. In the recently . . .