Association of Race and Ethnicity and Anticoagulation in Patients with Atrial Fibrillation Dually Enrolled in VA and Medicare: Effects of Medicare Part D on Prescribing Disparities.

Background: Racial and ethnic disparities in anticoagulation exist in atrial fibrillation (AF) management in Medicare and the Veterans Health Administration (VA), but the influence of dual VA and Medicare enrollment is unclear. We compared anticoagulant initiation by race and ethnicity in dually enrolled patients and assessed the role of Medicare Part D enrollment on anticoagulation disparities. Methods: We identified patients with incident AF (2014-2018) dually enrolled in VA and Medicare. We assessed any anticoagulant initiation (warfarin or direct-acting oral anticoagulants, DOACs) within 90 days of AF diagnosis and DOAC use among anticoagulant initiators. We modeled anticoagulant initiation, adjusting for patient, provider, and facility factors, including main effects for race and ethnicity and Medicare Part D enrollment and an interaction term for these variables. Results: In 43,789 patients, 8.9% were Black, 3.6% Hispanic, and 87.5% White; 10.9% participated in Medicare Part D. Overall, 29,680 (67.8%) patients initiated any anticoagulant, of which 17,568 (59.2%) initiated DOACs. Lower proportions of Black (65.2%) than Hispanic (67.6%) or White (68.0%) patients initiated any anticoagulant (p= 0.001), and lower proportions of Black (56.3%) and Hispanic (55.9%) than White (59.6%) patients (p=0.001) initiated DOACs. Compared to White patients, Black patients had significantly lower initiation of any anticoagulant, adjusted odds ratio (aOR) 0.89; 95% CI 0.82-0.97. The aORs for DOAC initiation were significantly lower for Black (0.72; 95% CI, 0.65-0.81) and Hispanic (0.84; 95% CI, 0.70-1.00) than White patients.The interaction between race and ethnicity and Medicare Part D enrollment was non-significant for any anticoagulant (p=0.99) and DOAC (p=0.27) therapies. Conclusions: In dually enrolled VA and Medicare patients with AF, Black patients were less likely to initiate any anticoagulant and Black and Hispanic patients were less likely to initiate DOACs. Medicare Part D enrollment did not moderate the associations between race and ethnicity and anticoagulant therapies.