Factor II antigen in liver disease and warfarin-induced vitamin K deficiency: Correlation with coagulant activity using echis venom

Abstract

Four coagulation factors (II, VII, IX, X) are synthesized in the liver as precursor forms. Vitamin K is necessary for their conversion to functional factors. Factor II precursor is antigenically similar to factor II and can be activated to form thrombin by Echis carinatus venom. Forty-one patients with liver disease and 30 patients with vitamin K deficiency (Warfarin treated), were compared with 51 normal patients. Rats with CCl₄-induced hepatic necrosis and animals given Warfarin were also studied. The following measurements were made: standard prothrombin time; Echis clotting time; factor II coagulant assay with thromboplastin; factor II assay with Echis venom; and factor II antigen (human) by electroimmunoassay. In animals and humans with liver disease, factor II was reduced, as measured by all techniques. With vitamin K deficiency functional factor II was reduced, but factor II antigen and Echis factor II activity were normal. The data suggest that the prothrombin time and Echis coagulation methods can be used to differentiate whether the coagulopathy in liver disease is due to reduced precursor levels of factor II, vitamin K deficiency (ie, impaired formation of functional from precursor factor II), or both.