title: Comparison of 1 month with 3 months of anticoagulation for a first episode of venous thromboembolism associated with a transient risk factor.
abstract: BACKGROUND
  The risk of recurrence is lower after treatment of an episode of venous thromboembolism associated with a transient risk factor, such as recent surgery, than after an episode associated with a permanent, or no, risk factor. Retrospective analyses suggest that 1 month of anticoagulation is adequate for patients whose venous thromboembolic event was provoked by a transient risk factor.
  
  
  METHODS
  In this double-blind study, patients who had completed 1 month of anticoagulant therapy for a first episode of venous thromboembolism provoked by a transient risk factor were randomly assigned to continue warfarin or to placebo for an additional 2 months. Our goal was to determine if the duration of treatment could be reduced without increasing the rate of recurrent venous thromboembolism during 11 months of follow-up.
  
  
  RESULTS
  Of 84 patients assigned to placebo, five (6.0%) had recurrent venous thromboembolism, compared with three of 81 (3.7%) assigned to warfarin, resulting in an absolute risk difference of 2.3%[95% confidence interval (CI) - 5.2, 10.0]. The incidence of recurrent venous thromboembolism after discontinuation of warfarin was 6.8% per patient-year in those who received warfarin for 1 month and 3.2% per patient-year in those who received warfarin for 3 months (rate difference of 3.6% per patient-year; 95% CI - 3.8, 11.0). There were no major bleeds in either group.
  
  
  CONCLUSIONS
  Duration of anticoagulant therapy for venous thromboembolism provoked by a transient risk factor should not be reduced from 3 months to 1 month as this is likely to increase recurrent venous thromboembolism without achieving a clinically important decrease in bleeding.
authors.affiliation: McMaster University, Hamilton, Ontario, Canada. kearonc@mcmaster.ca
authors.forename: C
authors.initials: C
authors.lastname: Kearon
authors.forename: J S
authors.initials: JS
authors.lastname: Ginsberg
authors.forename: D R
authors.initials: DR
authors.lastname: Anderson
authors.forename: M J
authors.initials: MJ
authors.lastname: Kovacs
authors.forename: P
authors.initials: P
authors.lastname: Wells
authors.forename: J A
authors.initials: JA
authors.lastname: Julian
authors.forename: B
authors.initials: B
authors.lastname: Mackinnon
authors.forename: C
authors.initials: C
authors.lastname: Demers
authors.forename: J
authors.initials: J
authors.lastname: Douketis
authors.forename: A G
authors.initials: AG
authors.lastname: Turpie
authors.forename: P
authors.initials: P
authors.lastname: Van Nguyen
authors.forename: D
authors.initials: D
authors.lastname: Green
authors.forename: J
authors.initials: J
authors.lastname: Kassis
authors.forename: S R
authors.initials: SR
authors.lastname: Kahn
authors.forename: S
authors.initials: S
authors.lastname: Solymoss
authors.forename: L
authors.initials: L
authors.lastname: Desjardins
authors.forename: W
authors.initials: W
authors.lastname: Geerts
authors.forename: M
authors.initials: M
authors.lastname: Johnston
authors.forename: J I
authors.initials: JI
authors.lastname: Weitz
authors.forename: J
authors.initials: J
authors.lastname: Hirsh
authors.forename: M
authors.initials: M
authors.lastname: Gent
mesh_terms: D000328:Adult; D000368:Aged; D017152:Antibodies, Antiphospholipid / Q000097:blood; D000925:Anticoagulants / Q000008:administration & dosage*; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D005260:Female; D006470:Hemorrhage / Q000209:etiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D017354:Point Mutation; D011516:Prothrombin / Q000235:genetics; D011956:Receptors, Cell Surface; D012307:Risk Factors; D055502:Secondary Prevention; D013923:Thromboembolism; D013997:Time Factors; D020246:Venous Thrombosis; D014859:Warfarin / Q000008:administration & dosage*
chemical_list: D017152:Antibodies, Antiphospholipid; D000925:Anticoagulants; D011956:Receptors, Cell Surface; C083864:factor V receptor, human; D014859:Warfarin; D011516:Prothrombin