title: Identifying unprovoked thromboembolism patients at low risk for recurrence who can discontinue anticoagulant therapy.
abstract: BACKGROUND
  Whether to continue oral anticoagulant therapy beyond 6 months after an "unprovoked" venous thromboembolism is controversial. We sought to determine clinical predictors to identify patients who are at low risk of recurrent venous thromboembolism who could safely discontinue oral anticoagulants.
  
  
  METHODS
  In a multicentre prospective cohort study, 646 participants with a first, unprovoked major venous thromboembolism were enrolled over a 4-year period. Of these, 600 participants completed a mean 18-month follow-up in September 2006. We collected data for 69 potential predictors of recurrent venous thromboembolism while patients were taking oral anticoagulation therapy (5-7 months after initiation). During follow-up after discontinuing oral anticoagulation therapy, all episodes of suspected recurrent venous thromboembolism were independently adjudicated. We performed a multivariable analysis of predictor variables (p < 0.10) with high interobserver reliability to derive a clinical decision rule.
  
  
  RESULTS
  We identified 91 confirmed episodes of recurrent venous thromboembolism during follow-up after discontinuing oral anticoagulation therapy (annual risk 9.3%, 95% CI 7.7%-11.3%). Men had a 13.7% (95% CI 10.8%-17.0%) annual risk. There was no combination of clinical predictors that satisfied our criteria for identifying a low-risk subgroup of men. Fifty-two percent of women had 0 or 1 of the following characteristics: hyperpigmentation, edema or redness of either leg; D-dimer > or = 250 microg/L while taking warfarin; body mass index > or = 30 kg/m(2); or age > or = 65 years. These women had an annual risk of 1.6% (95% CI 0.3%-4.6%). Women who had 2 or more of these findings had an annual risk of 14.1% (95% CI 10.9%-17.3%).
  
  
  CONCLUSIONS
  Women with 0 or 1 risk factor may safely discontinue oral anticoagulant therapy after 6 months of therapy following a first unprovoked venous thromboembolism. This criterion does not apply to men.
authors: Thrombosis Program, Division of Hematology, Department of Medicine, University of Ottawa, Ottawa, Ont. mrodger@ohri.ca
authors: Marc A
authors: MA
authors: Rodger
authors: Susan R
authors: SR
authors: Kahn
authors: Philip S
authors: PS
authors: Wells
authors: David A
authors: DA
authors: Anderson
authors: Isabelle
authors: I
authors: Chagnon
authors: Grégoire
authors: G
authors: Le Gal
authors: Susan
authors: S
authors: Solymoss
authors: Mark
authors: M
authors: Crowther
authors: Arnaud
authors: A
authors: Perrier
authors: Richard
authors: R
authors: White
authors: Linda
authors: L
authors: Vickars
authors: Tim
authors: T
authors: Ramsay
authors: Marisol T
authors: MT
authors: Betancourt
authors: Michael J
authors: MJ
authors: Kovacs
mesh_terms: D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000008:administration & dosage*; D000075202:Contraindications; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011446:Prospective Studies; D012008:Recurrence; D012307:Risk Factors; D013997:Time Factors; D016896:Treatment Outcome; D054556:Venous Thromboembolism / Q000175:diagnosis / Q000188:drug therapy*
chemical_list: D000925:Anticoagulants