Taipan viper venom and chromogenic substrate (chromozym Th). Prothrombin assay. No sensitivity to coumarin-induced prothrombin.

Prothrombin (factor II) was assayed in congenital or acquired prothrombin deficiencies and abnormalities using Taipan viper (Oxyuranus scutellatus) venom as activating agent and adsorbed normal plasma or a chromogenic compound (Chromozym-Th) as substrates. Prothrombin was found to be low, as expected in every instance, regardless of the substrate used. In coumarin treated patients the levels observed were similar to the prothrombin time percentile values and definitely lower than the immunological counterparts. Therefore, the Taipan viper venom appears suited for prothrombin assay even during anticoagulant therapy. Since the cost of the chromogenic substrate is about 20 times that of adsorbed normal plasma and since no special information is obtained by it, the use of the chromogenic method is not justified for routine purposes.