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 tre atment on coagulation parameters, 23 patients with venous thromboembolism w ere 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 a nother 4 weeks. Blood samples were taken at the end of each of these period s 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 tr eatment intensity. This was to some extent also true for the coagulation ac tivation markers, prothrombin fragment 1 + 2 and thrombin-antithrombin comp lex. Ratios of pro- and anticoagulant factors in some instances showed a de crease at therapeutical (International Normalised Ratio) levels, and also s ometimes with reduced warfarin treatment intensity. Taken together, our res ults encourage further research addressing issues of varying treatment inte nsity with warfarin and alternative methods for monitoring of anti-vitamin K treatment. (C) 2000 Elsevier Science Ltd. All rights reserved.