Thromb Haemostasis
-
The development of thrombosis in polycythaemia vera (PV) involves multifactorial processes including pathological activation of blood cells. Release of microparticles (MPs) by activated cells in diseases is associated with thrombotic risk, but relatively few data are available in PV. The aim of the present study was to investigate the increase in MP release and exposure of phosphatidylserine (PS) on the outer membrane of MP-origin cells in patients with PV, and to analyse their procoagulant activity (PCA). ⋯ Moreover, lactadherin competed factor V and VIII to PS and inhibited about 90% of the detected PCA in a dose-response manner while anti-TF antibody did no significant inhibition. Treatment with hydroxyurea is associated with a decrease in PS exposure and lactadherin+ MP release of erythrocytes/platelets. Our data demonstrate that PV patients are characterised by increased circulating procoagulant MPs and PS exposing erythrocytes/platelets, which could contribute to the hypercoagulable state in these patients.
-
A new ELISA (Zymutest HIA®), based on incubation of diluted plasma with protamine/heparin (PRT/H) complexes without and with platelet factor 4 (PF4) provided by a platelet lysate, was used to detect heparin-dependent antibodies in a cohort of 232 cardiac surgery (CS) patients and in 47 patients with heparin-induced thrombocytopenia (HIT). Significant binding of IgG/A/M to PRT/H complexes was demonstrated in 59 CS patients (25.4%), with similar absorbances whether platelet lysate was added to the plasma or not, and significant reactivity to PF4/H in 29 of them. Antibodies to PRT or heparin alone were present in 15 and two of these patients, respectively. ⋯ Therefore, a total of 35 CS patients exhibited dual antibody reactivity towards PRT/H and PF4/H complexes. Serotonin release assay performed with PRT alone was positive in 17 CS patients with antibodies to PRT/H, but all had normal platelet count evolution without thrombosis postoperatively. In conclusion, antibodies to PRT/H are frequently present in CS patients postoperatively (25.4%), and can activate platelets in vitro, but their clinical impact remains questionable.