Determination of prekallikrein in plasma by means of a chromogenic tripeptide substrate for plasma kallikrein.

A method for plasma prekallikrein determination utilizing a chromogenic tripeptic substrate is presented. The method has a good reproducibility and can easily be automized. Several parameters have been optimized. By using mixtures of deficient plasmas and pooled normal plasma or purified factors it was proved that prekallikrein was the factor determined and that more than 10% (of normal plasma concentration) of FXII and HMW kininogen were essential for the activation of prekallikrein in our method. Further experiments showed that the method was fairly selective and was not influenced by inhibitors present in normal plasma. The later finding was attributed to the high dilution of plasma made possible by using a potent activator and a sensitive substrate.