title: Quantitative one-stage assays for factors V and X.
abstract: The relative sensitivities of the prothrombin time, Russell's viper venom time and activated partial thromboplastin time were determined in one-stage quantitative assays for factor V and factor X. Sensitivity was defined as the slope of the reference curve. The prothrombin time was the most sensitive test for factor X and the least sensitive for factor V. The Russell's viper venom time was the most sensitive test for factor V and least sensitive for factor X. The activated partial thromboplastin time approximated the sensitivity of Russell's viper venom for factor V and had intermediate sensitivity for factor X. The data indicate that factor V is best quantitated by the Russell's viper venom time and factor X by the prothrombin time, exactly the opposite of what is customarily done.
mesh_terms: D001780:Blood Coagulation Tests / Q000379:methods; D005165:Factor V / Q000032:analysis*; D005170:Factor X / Q000032:analysis*; D006801:Humans; D011517:Prothrombin Time; D014688:Venoms
chemical_list: D014688:Venoms; D005165:Factor V; D005170:Factor X