title: Long-term risk of venous thrombosis after stopping anticoagulants for a first unprovoked event: A multi-national cohort.
abstract: BACKGROUND
  Choosing short-term (3-6 months) or indefinite anticoagulation after a first unprovoked venous thromboembolic event (VTE) is a common and difficult clinical decision. The long-term absolute risk of recurrent VTE after a first unprovoked VTE, in all patients and sub-groups, is not well established, hindering decision making.
  
  
  METHODS
  We conducted a multi-center multi-national prospective cohort study in first unprovoked VTE patients to establish the long-term risk of recurrent VTE after short-term anticoagulation in first unprovoked VTE patients (and sub-groups).We followed patients for symptomatic suspected VTE off of OAT. Suspected recurrent VTE was investigated with reference to baseline imaging and then independently and blindly adjudicated.
  
  
  RESULTS
  We recruited 663 participants between October, 2001 and March 2006 with the last follow-up in April 2014. During a mean 5.0 years of follow-up, 165/663 suspected VTE (in 408 patients) were adjudicated as recurrent VTE resulting in an annualized risk of recurrent VTE of 5.0% (95% CI: 4.2-5.8%) with a cumulative risk of 29.6% at 8 years. Men had a 7.6% (95% CI: 6.3-9.2%) annual risk of recurrent VTE. High risk women (2 or more HERDOO2 points; see text) had an annual risk of recurrent VTE of 5.9% (95% CI: 4.2-8.1%). Low risk women (1 or 0 HERDOO2 points) had 1.1% (95% CI: 0.6-2.0%) annual risk of recurrent VTE with a cumulative risk of 8.7% at 8 years.
  
  
  CONCLUSIONS
  Men and high risk women with unprovoked VTE should be considered for long-term anticoagulant therapy given a high risk of recurrent VTE after long-term follow-up. Women with a low HERDOO2 score may be able to safely discontinue anticoagulants.
  
  
  BACKGROUND
  This study was funded by the Canadian Institutes of Health Research (Grant # MOP 64319) and Heart and Stroke Foundation of Ontario (Grant # NA 6771). Registered at www.clinicaltrials.gov identifier: NCT00261014.
authors.affiliation: Thrombosis Program, Division of Hematology, Department of Medicine, University of Ottawa, Ottawa, Ontario, Canada; Clinical Epidemiology Program, Ottawa Health Research Institute, The Ottawa Hospital, Ottawa, Ottawa, Ontario, Canada. Electronic address: mrodger@ohri.ca.
authors.forename: Marc A
authors.initials: MA
authors.lastname: Rodger
authors.affiliation: Thrombosis Program, Division of Hematology, Department of Medicine, University of Ottawa, Ottawa, Ontario, Canada; Clinical Epidemiology Program, Ottawa Health Research Institute, The Ottawa Hospital, Ottawa, Ottawa, Ontario, Canada.
authors.forename: Dimitri
authors.initials: D
authors.lastname: Scarvelis
authors.affiliation: Department of Medicine, McGill University, Montreal, Canada; Centre for Clinical Epidemiology and Community Studies, Jewish General Hospital, Montreal, Canada.
authors.forename: Susan R
authors.initials: SR
authors.lastname: Kahn
authors.affiliation: Thrombosis Program, Division of Hematology, Department of Medicine, University of Ottawa, Ottawa, Ontario, Canada; Clinical Epidemiology Program, Ottawa Health Research Institute, The Ottawa Hospital, Ottawa, Ottawa, Ontario, Canada.
authors.forename: Philip S
authors.initials: PS
authors.lastname: Wells
authors.affiliation: Department of Medicine, Dalhousie University, Halifax, Nova Scotia.
authors.forename: David A
authors.initials: DA
authors.lastname: Anderson
authors.affiliation: Department of Medicine, Hôpital du Sacré-Coeur de Montréal, University of Montreal, Montreal, Canada.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Chagnon
authors.affiliation: Thrombosis Program, Division of Hematology, Department of Medicine, University of Ottawa, Ottawa, Ontario, Canada; Clinical Epidemiology Program, Ottawa Health Research Institute, The Ottawa Hospital, Ottawa, Ottawa, Ontario, Canada.
authors.forename: Grégoire
authors.initials: G
authors.lastname: Le Gal
authors.affiliation: Thrombosis Program, Division of Hematology, Department of Medicine, University of Ottawa, Ottawa, Ontario, Canada; Clinical Epidemiology Program, Ottawa Health Research Institute, The Ottawa Hospital, Ottawa, Ottawa, Ontario, Canada.
authors.forename: Esteban
authors.initials: E
authors.lastname: Gandara
authors.affiliation: Department of Medicine, McGill University, Montreal, Canada.
authors.forename: Susan
authors.initials: S
authors.lastname: Solymoss
authors.affiliation: Thrombosis Program, Division of Hematology, Department of Medicine, University of Ottawa, Ottawa, Ontario, Canada; Clinical Epidemiology Program, Ottawa Health Research Institute, The Ottawa Hospital, Ottawa, Ottawa, Ontario, Canada.
authors.forename: Elham
authors.initials: E
authors.lastname: Sabri
authors.affiliation: London Health Sciences Center, London, Ontario, Canada.
authors.forename: Judy
authors.initials: J
authors.lastname: Kovacs
authors.affiliation: Division of Hematology, Department of Medicine, University of Western Ontario, London, Ontario, Canada.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Kovacs
mesh_terms: D000925:Anticoagulants / Q000627:therapeutic use*; D002170:Canada / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012008:Recurrence; D012307:Risk Factors; D020246:Venous Thrombosis / Q000188:drug therapy* / Q000453:epidemiology / Q000473:pathology
chemical_list: D000925:Anticoagulants
keywords: Venous thrombosis; anticoagulants; prognosis; risk factors; therapy