Background: Although there exists potential risk of bleeding, extended 'lifelong' conventional-intensity [international normalized ratio (INR): 2.0-3.0] warfarin anticoagulation is recommended for unprovoked venous thromboembolism (VTE) patients because of risk of recurrent VTE. Whether long-term low-intensity (INR: 1.5-2.0) warfarin therapy reduced the risk of major bleeding without substantially lowered antithrombotic efficacy is not well understood. The aim of this study was to perform a systematic review and meta-analysis to evaluate the risk-benefits of low-intensity warfarin therapy.
Methods: We conducted a comprehensive search of electronic databases and included randomized control trials (RCTs) that reported efficacy (recurrent VTE) and safety (bleeding episodes) of low-intensity warfarin therapy compared with conventional-intensity warfarin or placebo from inception through Jun 2016.
Results: Four RCTs reporting high GRADE quality evidence were included. Although the relative risk of recurrent VTE with low-intensity therapy was significantly increased [2.96 (95% CI: 1.40 to 6.24), P < .004] compared to conventional-intensity warfarin, there was significant decrease of relative risk when compared with placebo [0.37 (95% CI: 0.24 to 0.56), P < .00001]. As per included publications, no significant major bleeding episodes were observed in low-intensity warfarin group.
Conclusions: Although less effective than conventional-intensity warfarin therapy this meta-analysis indicates that long-term low-intensity warfarin therapy is highly effective for preventing recurrent VTE than placebo, along with reduced risks of major bleeding and minimizing potential complications.
Keywords: anticoagulation; international normalized ratio; venous thromboembolism; warfarin.
© 2018 John Wiley & Sons Ltd.