Measurement of tissue plasminogen activator in plasma. a comparison of 3 methods and description of a new improved technique

Abstract

Three methods for measurement of tissue plasminogen activator (t-PA) activity in plasma were compared with regard to linearity, precision and clinical applicability. Based on this comparison a new improved technique is described. The 3 methods differed in the way the influence of inhibitors in plasma was eliminated. In method A t-PA was measured in acidified plasma, in method B in euglobulin precipitate and in method C after adsorption of plasma on lysine-Sepharose. After addition of 15 IU/ml of t-PA to normal plasma the recovery with method A was 17.4+2.4 IU/ml, with method B 11.4+0.5 IU/ml and with method C 9.8+0.9 IU/ml When tested on venous stasis plasma from 10 patients the 3 methods correlated well with a correlation coefficient of r = 0.97 – 0.99. Significantly higher values were found in acidified plasma (method A) as compared to the other methods. From this evaluation a method for determination of t-PA activity using acidification and internal standard to abolish the influence of inhibitors and poly-D-lysine as a stimulator was selected. The recovery with this method was 103.4+8.5% independent of PA inhibitor content in the plasma.