title: Recurrence of venous thromboembolism in patients with familial thrombophilia.
abstract: BACKGROUND
  Treatment of patients with deep vein thrombosis and an antithrombin or protein C or S deficiency is based on case reports and personal experience.
  
  
  OBJECTIVE
  To systematically assess the risk for recurrence of venous thromboembolism after a first episode in patients with these deficiencies, a literature review and retrospective family cohort study were performed.
  
  
  METHODS
  For the literature review, the annual incidence of a first recurrent venous thromboembolism was assessed for each deficiency by dividing the number of venous thromboembolic events by the number of years at risk. For the family cohort study, 1- and 5-year cumulative incidences of first recurrence were calculated based on medical histories taken in relatives of consecutive patients in whom venous thromboembolism and a deficiency were diagnosed.
  
  
  RESULTS
  For the literature review, the annual incidence of a first recurrent venous thromboembolism in patients with antithrombin or protein S deficiency ranged from 13% to 17% and 14% to 16%, respectively. For the family cohort study, the 1- and 5-year cumulative incidences of recurrent venous thromboembolism were 10% (95% confidence interval, 1%-19%) and 23% (95% confidence interval, 10%-36%), respectively. Warfarin sodium (Coumadin) prophylaxis was associated with 2 venous thromboembolic events in 141 years at risk (1.4% per year), in contrast with 19 events in 709 years at risk (2.7% per year) without prophylaxis (difference, -1.3%; 95% confidence interval, -3.5% to 1.0%).
  
  
  CONCLUSIONS
  The annual incidence of recurrent venous thromboembolism is high during the first years following a first episode, but seems to decline thereafter. Therefore, our results challenge current practice of prescribing lifelong warfarin therapy after a first or second episode of venous thromboembolism in patients with antithrombin or protein C or S deficiency.
authors.affiliation: Department of Clinical Epidemiology and Biostatistics, Academic Medical Centre, University of Amsterdam, The Netherlands.
authors.forename: A G
authors.initials: AG
authors.lastname: van den Belt
authors.forename: B J
authors.initials: BJ
authors.lastname: Sanson
authors.forename: P
authors.initials: P
authors.lastname: Simioni
authors.forename: P
authors.initials: P
authors.lastname: Prandoni
authors.forename: H R
authors.initials: HR
authors.lastname: Büller
authors.forename: A
authors.initials: A
authors.lastname: Girolami
authors.forename: M H
authors.initials: MH
authors.lastname: Prins
mesh_terms: D000925:Anticoagulants / Q000627:therapeutic use; D020152:Antithrombin III Deficiency; D015331:Cohort Studies; D006801:Humans; D015994:Incidence; D020151:Protein C Deficiency; D018455:Protein S Deficiency; D012008:Recurrence; D013923:Thromboembolism / Q000097:blood / Q000235:genetics* / Q000517:prevention & control; D019851:Thrombophilia / Q000097:blood / Q000150:complications* / Q000188:drug therapy / Q000235:genetics
chemical_list: D000925:Anticoagulants