ABSTRACT
Factor X (FX) and its activated version, FXa, are critical elements of the process of sustaining normal level of hemostasis. Factor X can be viewed as a gatekeeper of the coagulation pathway because it is responsible for converging extrinsic (tissue-factor dependent) and intrinsic (contact activation) pathway mechanisms. Due to the unique positions of FX and FXa in the coagulation cascade, it has been broadly accepted that modulating FXa activity can enable an effective control over thrombosis, which is a significant medical concern. Serious conditions, such as venous thromboembolism, can be successfully treated by administering specific FXa inhibitors. Currently three FXa inhibitors have been approved for clinical application and many more are in the development pipeline. Methods intended to determine anticoagulation activity of FXa inhibitors range from direct evaluation of coagulation potential to a direct assessment of FXa activity in the sample. Selection of an appropriate protocol with a high degree of predicting of FXa activity is critical during patient treatment and also for new drug development.
