[The study of Chinese optimal anticoagulant range of warfarin for venous thromboembolism]

The aim of trial is to observe the Chinese bleeding frequency and frequency of recurrent VTE in different international normalized ratio (INR) range of warfarin for venous thromboembolism (VTE) including deep venous thrombosis (DVT) and pulmonary embolism (PE), and to search optimal INR range.

We conducted a randomized, double-blind cohort trial, in which 180 patients were assigned to apply warfarin in a target INR of 1.50 to 1.99 (group A), a target INR of 2.00 to 2.50 (group B) or a target of INR of 2.51 to 3.00 (group C). Every group had respectively 60 patients. After they had completed warfarin therapy to be stability kept with those target INR range for two or more weeks, this study would be begun to observe the bleeding frequency and frequency of recurrent VTE.

There was significant difference in recurrent VTE frequency between Group A (8.3%) and BC (1.7%, P = 0.042). The minor bleeding frequency of Group A, B and C is respectively 8.3%, 18.3% and 6.7% (P = 0.089). The moderate bleeding frequency of Group A and BC is respectively 3.3% and 7.5% (P = 0.341), and large bleeding frequency of them is respectively 0% and 3.3% (P = 0.303). To patients whose age above 62 year, major bleeding episode occurred respectively in 1 patient assigned to INR of 1.5-2.5 and in three patients assigned to Group C (hazard ratio, 12. 600; 95 percent confidence interval, 1.183-134.238).

Warfarin therapy in INR of 2.0-3.0 is more effective than INR of 1.5-1.99 for the long-term prevention of recurrent VTE. And warfarin regimen in INR of 2.0-3.0 does not increase the risk of major bleeding either. So to general Chinese, INR ought to be recommended in 2.0-3.0. To patients whose age above 62 year, INR ought to be recommended between 2.0 to 2.5.