Correlation between different intensities of anti-vitamin K treatment and coagulation parameters

In order to study the effect of different intensities of anti-vitamin K treatment on coagulation parameters, 23 patients with venous thromboembolism were given, after the initial treatment period, warfarin at doses giving an International Normalised Ratio of 1.3-2.0 for 4 weeks, and of 1.1-1.3 for another 4 weeks. Blood samples were taken at the end of each of these periods and 4 weeks after the end of warfarin treatment. The vitamin K-dependent coagulation factors VII, IX, and X, as well as the inhibitor protein C and its cofactor protein S, all showed a highly significant correlation with treatment intensity. This was to some extent also true for the coagulation activation markers, prothrombin fragment 1+2 and thrombin-antithrombin complex. Ratios of pro- and anticoagulant factors in some instances showed a decrease at therapeutical (International Normalised Ratio) levels, and also sometimes with reduced warfarin treatment intensity. Taken together, our results encourage further research addressing issues of varying treatment intensity with warfarin and alternative methods for monitoring of anti-vitamin K treatment.