title: The clotting action of Russell viper venom. 1954.
abstract: Samuel I. Rapaport made seminal contributions to our basic understanding of blood coagulation. This paper beautifully illustrates his scientific approach through characterization of the clotting activity of venom from Daboia russelii, distinguishing it from the brain “thromboplastic” activity used in the prothrombin time. Using plasma from patients with deficiencies of proconvertin (factor VII), proaccelerin (factor V), antihemophilic globulin (factor VIII), or Christmas factor (factor IX), Rapaport and colleagues demonstrated that the venom's clotting activity does not require factor VII, but does require factor V and lipid. Thus, by combining the venom clotting test with the quick clotting time (prothrombin time), it was possible to diagnose factor VII deficiency. The venom is now known to act by directly activating factor X, and a form of the clotting test is used in the diagnosis of lupus anticoagulants.