title: Microparticle-associated tissue factor activity in patients with acute unprovoked deep vein thrombosis and during the course of one year.
abstract: BACKGROUND
  Tissue 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).
  
  
  OBJECTIVE
  To 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.
  
  
  METHODS
  In 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.
  
  
  RESULTS
  The 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.
  
  
  CONCLUSIONS
  MP-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.
authors.affiliation: Clinical Division of Haematology and Haemostaseology, Department of Medicine I, Medical University of Vienna, Austria.
authors.forename: Johannes
authors.initials: J
authors.lastname: Thaler
authors.affiliation: Clinical Division of Angiology, Department of Internal Medicine II, Medical University of Vienna, Austria.
authors.forename: Renate
authors.initials: R
authors.lastname: Koppensteiner
authors.affiliation: Clinical Division of Haematology and Haemostaseology, Department of Medicine I, Medical University of Vienna, Austria.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Pabinger
authors.affiliation: Clinical Division of Haematology and Haemostaseology, Department of Medicine I, Medical University of Vienna, Austria. Electronic address: cihan.ay@meduniwien.ac.at.
authors.forename: Cihan
authors.initials: C
authors.lastname: Ay
authors.affiliation: Clinical Division of Angiology, Department of Internal Medicine II, Medical University of Vienna, Austria.
authors.forename: Thomas
authors.initials: T
authors.lastname: Gremmel
mesh_terms: D000208:Acute Disease; D000328:Adult; D001777:Blood Coagulation; D055252:Cell-Derived Microparticles / Q000473:pathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D013925:Thromboplastin / Q000378:metabolism*; D020246:Venous Thrombosis / Q000097:blood* / Q000378:metabolism* / Q000473:pathology
chemical_list: D013925:Thromboplastin
keywords: Deep vein thrombosis; Lower limb; Microparticles; Tissue factor; Venous thromboembolism