Abstract P625: Differences in Urban/Rural Oral Anticoagulation and Mortality Among People With Incident Venous Thromboembolism: Medicare 20% Sample 2016-2018

Abstract

Introduction: Oral anticoagulants (OAC) are a standard and highly efficacious treatment for venous thromboembolism (VTE), with newer direct oral anticoagulants (DOACs; rivaroxaban and apixaban) equivalent or preferred over warfarin for many patients. Rural residents often lack easy access to medical care, which may cause differences in OAC use and outcomes in people with incident VTE. Hypothesis: People enrolled in Medicare who reside in rural locations will be less likely to be prescribed DOACs for primary treatment of incident VTE and will experience higher 6-month mortality compared to patients residing in urban areas. Methods: We used the Medicare 20% sample to identify a cohort of individuals aged ≥65 years with incident VTE and prescribed an OAC from 2016-2018. Risk factors, demographics, and ZIP codes to create urban/rural categories based on rural-urban commuting area codes were defined at time of VTE diagnosis. All-cause mortality and death date were ascertained via Medicare linkage to the Social Security Administration. Cox regression estimated hazard ratios (HRs) and 95% confidence intervals (95% CIs) for the association of urban/rural status and 6-month mortality rates, adjusting for demographics, comorbidities and medications. Urban/rural status and OAC choice were tested for multiplicative interaction. Results: Among 37,954 beneficiaries with VTE (mean age 76.7, SD 8.1), 82% were urban and 18% were rural. There were 3,778 deaths within 6 months of VTE diagnosis; 3,130 among urban residents while 649 among rural residents (83% vs. 17%). Overall, warfarin was prescribed more often in rural areas than urban areas (34% vs. 27%), rivaroxaban prescriptions were less common in rural versus urban areas (32% vs. 36%), and apixaban did not differ by rural versus urban status (35% vs. 37%). In multivariable-adjusted analyses, risk of mortality was not significantly different in rural versus urban areas (HR: 1.08 (0.99-1.17)). The HRs for mortality with rivaroxaban versus warfarin was 0.85 (95% CI: 0.79, 0.93), for apixaban versus warfarin it was 0.96 (95% CI: 0.89, 1.04), while for apixaban versus rivaroxaban it was 1.14 (95% CI: 1.05, 1.23). There was no interaction between OAC prescribed and urban/rural status for all comparisons of OACs (p-interaction rivaroxaban vs. warfarin: 0.50; apixaban vs. warfarin: 0.54; apixaban vs. rivaroxaban: 0.27). Conclusions: Rural versus urban residence resulted in less prescription of DOACs versus warfarin or oral anticoagulation treatment of VTE, but not a significant difference in 6-month mortality. The reasons for different prescribing patterns are unclear, whether due to comorbid conditions or provider knowledge. Greater attention to understanding rural-urban treatment differences is needed to ensure high quality care for everyone.