Apixaban associated with lower adverse event rates than warfarin in frail patients with afib

Frail Medicare beneficiaries with atrial fibrillation had lower rates of adverse events with apixaban versus warfarin, according to a recent study.

Researchers performed a 1:1 propensity score-matched analysis of Medicare data from 2010 to 2017 to compare outcomes of direct oral anticoagulants (DOACs) with warfarin in patients with atrial fibrillation according to levels of frailty. The study included Medicare beneficiaries with atrial fibrillation who had started therapy with apixaban, rivaroxaban, dabigatran, or warfarin. The composite end point was death, ischemic stroke, or major bleeding by frailty levels, which were determined by a claims-based frailty index. The study results were published July 20 by Annals of Internal Medicine.

In the cohort of 158,730 patients taking dabigatran or warfarin, who were followed for a median of 72 days, the event rate per 1000 person-years was 63.5 for those starting dabigatran and 65.6 for those starting warfarin (hazard ratio [HR], 0.98 [95% CI, 0.92 to 1.05]; rate difference [RD], −2.2 [95% CI, −6.5 to 2.1]). The HRs were 0.81 (95% CI, 0.68 to 0.97), 0.98 (95% CI, 0.90 to 1.08), and 1.09 (95% CI, 0.96 to 1.23) for nonfrail, prefrail, and frail patients, respectively. For the cohort of 275,944 patients taking rivaroxaban or warfarin, who were followed for a median of 82 days, the event rate per 1000 person-years was 77.8 for those starting rivaroxaban and 83.7 for those starting warfarin (HR, 0.98 [95% CI, 0.94 to 1.02]; RD, −5.9 [95% CI, −9.4 to −2.4]). HRs were 0.88 (95% CI, 0.77 to 0.99), 1.04 (95% CI, 0.98 to 1.10), and 0.96 (95% CI, 0.89 to 1.04) for nonfrail, prefrail, and frail patients, respectively. Finally, in the cohort of 218,738 patients taking apixaban or warfarin, who were followed for a median of 84 days, the event rate per 1000 person-years was 60.1 for those starting apixaban and 92.3 for those starting warfarin (HR, 0.68 [95% CI, 0.65 to 0.72]; RD, −32.2 [95% CI, −36.1 to −28.3]). HRs were 0.61 (95% CI, 0.52 to 0.71), 0.66 (95% CI, 0.61 to 0.70), and 0.73 (95% CI, 0.67 to 0.80) for nonfrail, prefrail, and frail patients, respectively.

The authors acknowledged that direct comparison among DOACs was not possible and that frailty is not assessed routinely in clinical practice, among other limitations. “In conclusion, our study provides evidence to guide the choice of a DOAC versus warfarin for older adults with [atrial fibrillation],” the authors wrote. “Only apixaban was consistently associated with lower rates of the composite end point of death, ischemic stroke, and major bleeding than warfarin across all frailty levels.”