Abstract 16370: Real-World Risk of Thromboembolism or Bleeding with Warfarin or Dabigatran Therapy in Patients with Atrial Fibrillation

Abstract

Background: Dabigatran and warfarin are indicated for stroke prevention in patients with non-valvular atrial fibrillation (AFIB), but their real-world comparative effectiveness and safety are unknown.

Methods: A retrospective analysis of a de-identified, integrated pharmacy-medical claims database was conducted in patients with AFIB and new to either dabigatran or warfarin (no anticoagulant therapy 6-months prior) during 1/1/10 to 2/28/11. Patients with continuous eligibility of ≥12 months prior and 4 months post index anticoagulant prescription claim date were included. Disease states, CHA₂DS₂VASc, and ATRIA risk scores were determined using demographic data and ICD-9/CPT codes (≥2 separate dates) in the prior 12 months. Stroke/systemic embolism (SysEmb) and bleeding hospitalizations (per RE-LY) in the 4-months post anticoagulant index were determined via claims and stratified by baseline risk and anticoagulant used.

Results: A total of 8,162 AFIB patients received either warfarin (N=7072) or dabigatran (N=1090) (TABLE). Compared to warfarin, patients receiving dabigatran were younger, male, had higher out-of-pocket costs, and lower event risk by CHA₂DS₂VASc and ATRIA risk scores. Overall 4-month event rates on anticoagulants were high: stroke/SysEmb, 2%; and, bleeding 3.7%. Increasing CHA₂DS₂VASc and ATRIA risk scores were positively associated with increasing risk rates of stroke/systemic embolism, or bleeding (p < 0.001). ATRIA further differentiated bleeding between low- and moderate-risk subjects versus high-risk subjects. After adjustment, there was no difference in stroke/SysEmb or bleeding between anticoagulants.

Conclusion: The real-world stroke/SysEmb and bleeding risks among patients receiving warfarin and dabigatran are greater than observed in AFIB clinical trials. Risk-adjusted stroke/SysEmb and bleeding outcomes did not differ between warfarin and dabigatran, but additional surveillance is warranted.