Safety, effectiveness, and health care cost comparisons among elderly patients with venous thromboembolism prescribed warfarin or apixaban in the United States Medicare population

Objective: To compare safety, effectiveness, and healthcare costs of major bleeding (MB), clinically relevant non-major (CRNM) bleeding, recurrent venous thromboembolism (VTE), and all-cause hospitalization among elderly Medicare VTE patients prescribed warfarin vs apixaban. Methods: Using 100% Medicare data, elderly patients prescribed apixaban or warfarin within 30 days after a VTE encounter were identified. Patients had continuous health plan enrollment and no parenteral or oral anticoagulant use ≤6 months preceding the VTE encounter. Cohorts were balanced using 1:1 propensity score matching (PSM). Cox proportional hazard models were used to assess the risk of MB, CRNM bleeding, recurrent VTE, and all-cause hospitalization. Generalized linear and two-part models were used to estimate MB-, recurrent VTE-, and all-cause related costs (per patient per month [PPPM]). Results: In the pre-matched cohort, 25,284 (66.9%) patients were prescribed warfarin and 12,515 (33.1%) apixaban. After 1:1 PSM, 11,363 matched pairs of apixaban-warfarin patients were included for a mean follow-up of 4.0 and 4.4 months, respectively. Matched cohorts had a mean age of 78 years and mean Charlson Comorbidity Index score of 2.9. Warfarin was associated with a higher risk of MB (hazard ratio [HR] = 1.31; 95% confidence interval [CI] = 1.10–1.57) and CRNM bleeding (HR = 1.31; 95% CI = 1.19–1.43) vs apixaban. The risks of recurrent VTE (HR = 0.96; 95% CI = 0.70–1.33) and all-cause hospitalization (HR = 1.05; 95% CI = 0.99–1.12) were similar among warfarin and apixaban patients. Warfarin patients had higher MB-related ($147 vs $75; p =.003) and all-cause costs PPPM ($3,267 vs $3,033; p <.001), but similar recurrent VTE-related medical costs PPPM ($30 vs $36; p =.516) vs apixaban patients. Conclusions: Warfarin was associated with significantly higher risk of MB and CRNM bleeding as well as higher MB-related and all-cause costs vs apixaban patients. Recurrent VTE risk and costs were similar among warfarin and apixaban patients.