Effectiveness and safety of outpatient rivaroxaban versus warfarin for treatment of venous thromboembolism in patients with a known primary hypercoagulable state.

INTRODUCTION: Screening for primary hypercoagulable states (PHSs) in venous thromboembolism (VTE) patients was not mandated in the EINSTEIN trials; and therefore, few patients with a known PHS were available for analysis. We sought to assess the effectiveness and safety of rivaroxaban versus warfarin for treatment of VTE in patients with a known PHS.

METHODS: Using MarketScan claims data from 1/2012-9/2015, we identified adults with a primary diagnosis of VTE during a hospitalization/emergency department visit (the index event), with ≥180-days of continuous insurance coverage prior to the index event, a documented diagnosis for a PHS and newly-initiated as an outpatient on rivaroxaban or warfarin within 30-days of the index VTE. Rivaroxaban and warfarin users were 1:1 propensity-score matched. Balance between cohorts was evaluated by inspecting standardized differences for baseline covariates (<0.1 considered well-balanced). Patients were followed up to 12-months from the index event or until occurrence of an endpoint, switch/discontinuation of index oral anticoagulation or insurance disenrollment. Rates of recurrent VTE and major bleeding were compared using Cox regression and reported as hazard ratios (HRs) with 95% confidence intervals (CIs).

RESULTS: We matched 403 rivaroxaban and 403 warfarin patients with VTE and a known PHS. All baseline covariates had a standardized difference < 0.1. Rivaroxaban use was associated with a non-significant reduction in recurrent VTE (HR = 0.70, 95%CI = 0.33-1.49) and major bleeding (HR = 0.55, 95%CI = 0.16-1.86) versus warfarin.

CONCLUSIONS: In routine practice, the effectiveness and safety of rivaroxaban versus warfarin in VTE patients with a known PHS appears to be similar to that observed in the EINSTEIN trial program.