Adherence with oral anticoagulation in non-valvular atrial fibrillation: a comparison of vitamin K antagonists and non-vitamin K antagonists

Aims: The purpose of this study was to describe adherence with non-vitamin K antagonists (NOACs) and vitamin K antagonists (VKA) in patients with non-valvular atrial fibrillation (NVAF).

Methods and results: By linkage of Danish nationwide registers, we identified patients with NVAF who claimed a prescription of a NOAC (dabigatran, rivaroxaban, and apixaban), or a VKA. Adherence was evaluated according to Proportions of Days Covered, refill gaps, and switch in treatment. Adjusted analyses were calculated with logistic regression and Cox proportional hazard models. Between 2011 and 2014, 46 675 patients with NVAF claimed a prescription of anticoagulation (OAC): 57.3% used VKA, 29.8% dabigatran, 8.5% rivaroxaban, and 4.4% apixaban. During the first 180 days, PDC >80% was the highest among users of rivaroxaban. Compared with rivaroxaban, OR was 0.79 with apixaban (95% CI 0.69-0.92), 0.72 with dabigatran (95% CI 0.66-0.80), and 0.76 with VKAs (95% CI 0.69-0.83). HR for refill gaps between 7 and 89 days of length were (rivaroxaban as reference): apixaban 1.52(95% CI 1.36-1.69), dabigatran 1.72 (95% CI 1.60-1.85), and VKA 2.36(95% CI 2.20-2.52). Refill gaps of more than 89 days occurred in 11.5% of VKA recipients, with substantially lower rates for patients treated with NOAC. Switch between OACs was the highest in users of dabigatran (21.0%) and the lowest in users of apixaban (8.6%).

Conclusion: Among NVAF patients treated with OAC, 42.7% received a NOAC. PDC > 80%, and periods without refill gaps were the highest among users of rivaroxaban. Refill gaps occurred most often with VKA, switch was most common with dabigatran use.