Microparticle-associated tissue factor activity in patients with acute unprovoked deep vein thrombosis and during the course of one year

•Elevated tissue factor (TF)-bearing microparticles (MPs) have been found in different prothrombotic conditions•We hypothesized that MP-associated TF activity may contribute to the pathogenesis of unprovoked deep vein thrombosis (DVT).•MP-TF activity did not differ between patients with acute DVT and healthy controls•No changes in MP-TF activity were found in four follow-up measurements during one year

BackgroundTissue factor (TF) is the main in-vivo initiator of blood coagulation. Microparticles (MPs) are small procoagulant membrane vesicles. Elevated TF-bearing MPs have been found in different prothrombotic conditions and MP-associated TF activity may contribute to the pathogenesis of unprovoked deep vein thrombosis (DVT).ObjectiveTo determine MP-TF activity levels at diagnosis of DVT and at four additional time points during the course of one year in a well-defined group of patients with unprovoked DVT of the lower limb.Patients/MethodsIn this study, 41 patients with acute unilateral symptomatic and unprovoked DVT of the lower limb were included and followed for 1 year. Venous blood samples for determination of MP-TF activity were drawn at diagnosis of acute DVT, and 1-, 3-, 6-, and 12 months later. In addition, 10 young and healthy control subjects were included.ResultsThe median MP-TF activity was 0.06 pg/mL (25th-75th percentile: 0.0-0.53) in patients with acute DVT and 0.18 pg/mL (0.07-0.33) in healthy controls, and did not differ significantly (p = 0.35). No significant changes in MP-TF activity were found in the follow-up measurements. MP-TF activity did also not differ significantly between patients with proximal- or distal DVT and between those with- or without residual DVT after 6 months.ConclusionsMP-TF activity is low at the acute event in patients with unprovoked DVT of the lower limb and remains unchanged during the course of the disease. Our data do not support the hypothesis that TF-bearing MPs play a determining role in the pathogenesis of unprovoked DVT.