A Simple Rapid Method for Estimating Serum Plasmin Activity with Fibrin-coated Latex Particles.

CCURATE semiquantitative assessment cf fibrinolytic activity in blood serum has usually involved the use of complicated technical procedures and specialized apparatus. Alkjaersig1 estimated fibrinolytic activity from the amount of P31-labeled fibrin which was released from a standardized clot. Astrup2 measured the zone of lysis produced by plasmin activity on a standardized fibrin plate, produced by coagulation of fibrinogen with thrombin. Blix3 estimated clot lysis from the release of red cells and consequent change in supernatant hemoglobin from a performed standard clot. Other technics include the photometric method of Grossen,6 using paper fibrinolysis, the thromboelastographic monitoring of clot lysis used by Von Kaulla7 and the coagulated bovine plasma system used by Kontinen.8 The above methods are useful in research work, but are not well suited for the routine clinical laboratory, where plasmin activity is most often estimated by the lysis time of a standard fibrin clot; this is a rather coarse method requiring considerable amounts of time and material. Recently the author introduced an immunologic test for detecting degraded fibrin products in vivo4’5 which indirectly corresponds to plasmin activity. A method is now proposed for directly estimating this activity in vitro by means cf a modified latex fixation test. Latex particles previously coated with human fibrinogen are mixed with the test serum. The addition of thrombin to the mixture causes the fibrinogen to polymerize into fibrin filaments, which aggregate the latex particles into solid clumps. If the serum is actively fibrinolytic the fibrin filaments are rapidly dissolved, releasing free latex particles into suspension into the serum and producing turbidity that can be measured.