PLATELET-FACTOR-3 IN PLASMA FRACTIONS - ITS RELATION TO MICROPARTICLESIZE AND THROMBOSES

Platelet factor 3 (PF3) was assayed by Russell's viper venom (RVV) in three plasma fractions, platelet-rich plasma (PRP), platelet poor plas ma (PPP), and 0.1 mu m particle-filtered plasma (PFP), in 42 healthy c ontrols, 34 patients with recent cerebrovascular accidents (CVA) and 2 8 with recent ischemic events from coronary artery disease (CAD). Plat elet microparticles (PMP) were assayed in PPP by flow cytometry. Relat ive to controls, the RVV clotting times were shortened in all three pl asma fractions in both patient groups, p < 0.001. PMP were also elevat ed in both patient groups, p < 0.001. Linear regression analysis showe d that the RVV times of PPP are inversely correlated with PMP, p < 0.0 05, in patient groups but not in controls. There was no correlation of RVV time with PT, APTT or FIB. After converting RVV times to units of PF3 activity, it could be shown that only about 1/4 of the total PF3 activity was contributed by platelets. The major contribution to the P F3 activity in controls was from microparticles < 0.1 mu m but in pati ents was due mainly to microparticles > 0.1 mu m The RVV time was supe rior to routine coagulation tests in discriminating thrombotic patient s from healthy controls.