title: Factors that predict risk of thrombosis in relatives of patients with unprovoked venous thromboembolism.
abstract: BACKGROUND
  Factors that predict the risk of venous thromboembolism in the first-degree relatives of patients with unprovoked venous thromboembolism are uncertain but important for counseling. We aimed to identify risk factors for, and quantify the risk of, venous thromboembolism in first-degree relatives of patients (index case patients) with a first episode of unprovoked venous thromboembolism.
  
  
  METHODS
  In a cross-sectional study, using a standardized method and without knowledge of whether patients or their relatives had thrombophilia, we assessed the prevalence of previous venous thromboembolism in 1,916 first-degree relatives of 378 unselected patients with a first episode of unprovoked venous thromboembolism. Patient characteristics, and the presence of factor V Leiden or the G20210A prothrombin gene mutation in patients, were assessed as predictors of venous thromboembolism in patient's relatives.
  
  
  RESULTS
  There were 102 previous episodes of venous thromboembolism in the first-degree relatives (prevalence, 5.3%). Thrombosis at a young age in patients was the strongest predictor of venous thromboembolism in relatives, with an adjusted odds ratio (OR) for younger patients (ie, patients < 45 years of age when venous thromboembolism occurred; lowest quartile) compared with older patients (ie, patients > 71 years of age; highest quartile) of 3.27 (95% CI, 1.68 to 6.38). The presence of factor V Leiden or the G20210A prothrombin gene in patients was a weak independent predictor of venous thromboembolism in relatives (adjusted OR, 1.48; 95% CI, 0.94 to 2.33).
  
  
  CONCLUSIONS
  Unprovoked venous thromboembolism at a young age is associated with a substantially increased risk of venous thromboembolism in patients' families.
authors: Department of Internal Medicine and Chest Diseases, Groupe d'Etude de la Thrombose de Bretagne Occidentale, Brest, France. Electronic address: francis.couturaud@chu-brest.fr.
authors: Francis
authors: F
authors: Couturaud
authors: Department of Internal Medicine and Chest Diseases, Groupe d'Etude de la Thrombose de Bretagne Occidentale, Brest, France.
authors: Christophe
authors: C
authors: Leroyer
authors: McMaster University and the Henderson Research Centre, Hamilton, ON, Canada.
authors: Jim A
authors: JA
authors: Julian
authors: McGill University, Montreal, QC, Canada.
authors: Susan R
authors: SR
authors: Kahn
authors: McMaster University and the Henderson Research Centre, Hamilton, ON, Canada.
authors: Jeffrey S
authors: JS
authors: Ginsberg
authors: Ottawa University, Ottawa, ON, Canada.
authors: Philip S
authors: PS
authors: Wells
authors: McMaster University and the Henderson Research Centre, Hamilton, ON, Canada.
authors: James D
authors: JD
authors: Douketis
authors: Department of Internal Medicine and Chest Diseases, Groupe d'Etude de la Thrombose de Bretagne Occidentale, Brest, France.
authors: Dominique
authors: D
authors: Mottier
authors: McMaster University and the Henderson Research Centre, Hamilton, ON, Canada.
authors: Clive
authors: C
authors: Kearon
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D003430:Cross-Sectional Studies; D005165:Factor V / Q000235:genetics*; D005190:Family; D005260:Female; D005817:Genetic Counseling; D020022:Genetic Predisposition to Disease / Q000235:genetics; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009154:Mutation / Q000235:genetics*; D011237:Predictive Value of Tests; D011516:Prothrombin / Q000235:genetics*; D012189:Retrospective Studies; D012307:Risk Factors; D013927:Thrombosis / Q000453:epidemiology*; D054556:Venous Thromboembolism / Q000453:epidemiology* / Q000235:genetics*
chemical_list: C095381:factor V Leiden; D005165:Factor V; D011516:Prothrombin