The Two-Stage “Prothrombin” Assay in Study of Bleeding and Clotting Disorders §

Recent study of 400 human cases, including 240 with diverse hemorrhagic disorders, has accumulated noteworthy experience with a wide variety of test methods for quantitating the collective and individual factors in the blood clotting and hemostatic mechanisms. Important among these tests are those dealing with prothrombin and its conversion to thrombin for the enzymatic polymerization of fibrinogen to fibrin clot. The so-called "prothrombin time" test, originated by Quick et al.,2" has been compared in this investigation with three specific prothrombin methods. Ware and Seegers2' made detailed studies of the technical aspects of the "2-stage" prothrombin assay method originated by Warner ,Brinkhous, and Smith.' The present communication deals with our experience bearing on the validity of this method and its modifications, including some of our own, based uponl experiments of a technical nature, with the opportunities for using test plasmas and sera from a representative collection of cases with bleeding disorders.