On the reliability of plasminogen measurement employing the proactivator-activator converting method

Abstract

A simple plasminogen determination method is presented. It is based upon the conversion of plasminogen into activator by large and constant amounts of streptokinase. The activator contained in a standard coagulum consisting of bovine fibrin, streptokinase, and a 1:40 dilution of human plasma converts the plasminogen adsorbed on bovine fibrin into plasmin. Lysis of the test coagulum is hereby induced. The speed of such lysis is limited by the concentration of the activator incorporated in the test coagulum. The variable component of the activator being human plasminogen, the speed of lysis is directly dependent upon the concentration of human plasminogen in the standard coagulum. Using the thromboelastograph according to Hartert in recording the test clot lysis times, this method of plasminogen determination was shown to be a simple and quick procedure. The standard deviation ranged from +/- 13,2 tp 68%, depending upon the plasminogen value to be measured (lower rates of error were attached to high, and higher rates of error to low, plasminogen concentrations). The biological variation of plasminogen values in a group of 26 men aged from 40 to 65 years was calculated to be +/- 21%. Both plasminogen and plasmin, its activated form, were exchangeable in the test, i.e. plasminogen determinations performed by activator assay did not differentiate between plasminogen and plasmin. There was no influence by varying anti-SK titers in the plasma up to a circulating antibody content of 2 million. Furthermore, plasma antiplasmins did not affect the plasminogen measuring system. Plasminogen tested by activator assay displayed values closely related to those achieved by immunochemical methods. Plasminogen measurements were performed in patients undergoing streptokinase and urokinase infusion treatment. 5,000 u streptokinase per hour, as well as 270,000 CTA-u urokinase per hour, infused over a period of 2 days produced a fall in plasminogen down to 30-60% of normal. In contrast, 100,000 u streptokinase per hour lowered the plasminogen concentration down to values of below 1%. The foregoing data indicate that plasminogen measurement, according to the principles outlined here (activator assay), may be regarded as a valuable and reliable method for the routine control of streptokinase and urokinase therapy.