Bleeding Risk with Apixaban vs. Rivaroxaban in Acute Venous Thromboembolism

To the Editor: The Comparison of Bleeding Risk between Rivaroxaban and Apixaban (COBRRA) trial by Castellucci et al. (March 12/19 issue) 1 established the superiority of apixaban over rivaroxaban with regard to bleeding risk among patients with acute venous thromboembolism (VTE). However, a critical confounding variable — the difference in medication adherence — warrants discussion. The article mentions that “complete adherence” was reported by 65.7% of the patients in the apixaban group and by 75.1% of those in the rivaroxaban group. This gap of 9.4 percentage points is likely to be attributable to the twice-daily regimen of apixaban as compared with . . .