title: Influence of preceding length of anticoagulant treatment and initial presentation of venous thromboembolism on risk of recurrence after stopping treatment: analysis of individual participants' data from seven trials.
abstract: OBJECTIVE
  To determine how length of anticoagulation and clinical presentation of venous thromboembolism influence the risk of recurrence after anticoagulant treatment is stopped and to identify the shortest length of anticoagulation that reduces the risk of recurrence to its lowest level.
  
  
  METHODS
  Pooled analysis of individual participants' data from seven randomised trials.
  
  
  METHODS
  Outpatient anticoagulant clinics in academic centres.
  
  
  METHODS
  2925 men or women with a first venous thromboembolism who did not have cancer and received different durations of anticoagulant treatment.
  
  
  METHODS
  First recurrent venous thromboembolism after stopping anticoagulant treatment during up to 24 months of follow-up.
  
  
  RESULTS
  Recurrence was lower after isolated distal deep vein thrombosis than after proximal deep vein thrombosis (hazard ratio 0.49, 95% confidence interval 0.34 to 0.71), similar after pulmonary embolism and proximal deep vein thrombosis (1.19, 0.87 to 1.63), and lower after thrombosis provoked by a temporary risk factor than after unprovoked thrombosis (0.55, 0.41 to 0.74). Recurrence was higher if anticoagulation was stopped at 1.0 or 1.5 months compared with at 3 months or later (hazard ratio 1.52, 1.14 to 2.02) and similar if treatment was stopped at 3 months compared with at 6 months or later (1.19, 0.86 to 1.65). High rates of recurrence associated with shorter durations of anticoagulation were confined to the first 6 months after stopping treatment.
  
  
  CONCLUSIONS
  Three months of treatment achieves a similar risk of recurrent venous thromboembolism after stopping anticoagulation to a longer course of treatment. Unprovoked proximal deep vein thrombosis and pulmonary embolism have a high risk of recurrence whenever treatment is stopped.
authors: Hospices Civils de Lyon, Service de Biostatistique, UMR, CHU de Lyon, France.
authors: Florent
authors: F
authors: Boutitie
authors: Laurent
authors: L
authors: Pinede
authors: Sam
authors: S
authors: Schulman
authors: Giancarlo
authors: G
authors: Agnelli
authors: Gary
authors: G
authors: Raskob
authors: Jim
authors: J
authors: Julian
authors: Jack
authors: J
authors: Hirsh
authors: Clive
authors: C
authors: Kearon
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