High plasma levels of plasminogen activator inhibitor 1 (PAI-1) in polycythemia vera and essential thrombocythemia are associated with thrombosis.

We attempted to determine if a hypercoagulability state exists in patients with polycythemia vera (PV) and essential thrombocythemia (ET). We studied the hematocrit level, platelet count, use of any antiaggregant drugs, thrombotic or bleeding accidents and plasma levels of antithrombin III, protein C, total protein S, free protein S, vWF:Ag (Von Willebrand's factor related antigen), thrombin-antithrombin complexes, D-dimer, fibrinolytic activity, tissue plasminogen activator, plasminogen and PAI-1 in 33 patients (19 with ET and 14 with PV). PAI-1 plasma concentration was significantly higher in, both ET and PV patients than in the control group, and were higher in those patients with previous thrombotic episodes than in asymptomatic patients or with previous bleeding episodes. Increasing age was associated to more thrombotic episodes while younger patients presented with more hemorrhagic complications. A linear correlation between platelet count and PAI-1 levels in PV patients (r = 0.44, p < 0.05) and ET patients (r = 0.30, p < 0.05) was found. Fibrinolytic activity in patients with ET was significantly decreased when compared to the control group. A hypofibrinolytic state could be an additional factor which could be used as a predictive index of the thrombotic or bleeding tendency in each patient.