Aim: Although warfarin remains important despite the widespread use of nonvitamin K antagonist oral anticoagulants (NOACs), to date, the reality of warfarin use in the “NOACs era” is unclear. This multicenter observational study aimed to clarify the key factors contributing to warfarin treatment stability. Methods: The practical use of warfarin, stability of warfarin therapy, and factors contributing to this stability were investigated in community-based hospitals through a real-world study. Clinical data were retrospectively extracted from the medical records of warfarin-treated Japanese patients (age, 71.3±5.5 years) with atrial fibrillation (AF), prosthetic heart valve, or other concerns requiring anticoagulation. Treatment stability was considered as time in therapeutic range of international normalized ratio of prothrombin time (TTR: %). The factors contributing to TTR were investigated, including CHADS2 score components. Results: Mean CHADS2 score was highest (1.38±0.88, p＜0.001), and most CHADS2 score components in addition to hepatorenal dysfunction were factors contributing to the low TTR in patients with AF (n =176). The similarity was found in overall patients who were prescribed warfarin (n = 518). TTR decreased according to the CHADS2 score component accumulation. Gender, dose and prescription interval of warfarin, and co-administration of antiplatelet agents did not correlate with the low TTR. Conclusions: This retrospective study demonstrated that the CHADS2 score component accumulation and hepatorenal dysfunction are factors significantly contributing to the low TTR, which is indicative of poor warfarin treatment stability, in patients such as those with AF.
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