Snake venoms have evolved primarily to immobilize and kill prey, and consequently, they contain some of the most potent natural toxins. Part of that armory is a range of hemotoxic components that affect every area of hemostasis, which we have harnessed to great effect in the study and diagnosis of
hemostatic disorders. The most widely used are those that affect coagulation, such as
thrombin-like
enzymes unaffected by
heparin and
direct thrombin inhibitors, which can help confirm or dispute their presence in plasma. The liquid
gold of coagulation activators is
Russell's viper venom, since it contains activators of
factor X and
factor V. It is used in a range of clotting-based assays, such as assessment of
factor X and
factor V deficiencies,
protein C and
protein S deficiencies,
activated protein C resistance, and probably the most important test for lupus
anticoagulants, the dilute Russell's viper venom time. Activators of
prothrombin, such as oscutarin C from Coastal Taipan
venom and
ecarin from saw-scaled viper
venom, are employed in
prothrombin activity assays and
lupus anticoagulant detection, and
ecarin has a valuable role in quantitative assays of
direct thrombin inhibitors.
Snake venoms affecting primary hemostasis include
botrocetin from the jararaca, which can be used to assay
von Willebrand factor activity, and
convulxin from the cascavel, which can be used to detect deficiency of the platelet
collagen receptor,
glycoprotein VI. This article takes the reader to every area of the diagnostic hemostasis laboratory to appreciate the myriad applications of
snake venoms available in diagnostic practice.