Impact of Direct Oral Anticoagulant Off-Label Reduced Dose in Combination With Antiplatelet Agents on Clinical Outcome　― Propensity Score-Matching Analysis From the DIRECT Real-World Non-Valvular Atrial Fibrillation Registry ―

Background: The association between direct oral anticoagulant (DOAC) dose and clinical outcomes when used with antiplatelets still remains to be investigated. Methods and Results: We conducted a prospective registry of non-valvular atrial fibrillation (AF) patients with DOAC: the DIRECT registry (n=2,216; follow-up, 407±388 days). We analyzed patients taking standard dose (n=907) and off-label reduced dose (n=338) DOAC in this sub-analysis. These patients were further stratified by add-on antiplatelets. Because DOAC dose was not randomly selected, potential confounding factors were eliminated through a propensity score-matching technique. The primary endpoint was clinically significant bleeding. The secondary endpoint was major adverse cardiovascular events (MACE; composite of all-cause death, all myocardial infarction, and stroke/systemic embolism). In patients with DOAC only/DOAC+antiplatelets, we successfully matched 212/62 patients who received off-label reduced dose DOAC with 212/62 standard dose patients. Off-label DOAC dose reduction did not have a significant impact on bleeding (HR, 1.123; 95% CI: 0.730–1.728, P=0.596) or MACE (HR, 1.107; 95% CI: 0.463–2.648, P=0.819) in patients with DOAC only, whereas in patients with add-on antiplatelets, off-label dose reduction significantly reduced bleeding (HR, 0.429; 95% CI: 0.212–0.868, P=0.019) without increasing MACE (HR, 2.205; 95% CI: 0.424–11.477, P=0.348). Conclusions: Reduced DOAC dose in combination with antiplatelet agents was associated with fewer bleeding complications than standard-dose therapy with no reduction in efficacy.