title: Familial thrombophilia and lifetime risk of venous thrombosis.
abstract: BACKGROUND
  We started a large multicenter prospective follow-up study to provide reliable risk estimates of venous thrombosis in families with various thrombophilic defects.
  
  
  OBJECTIVE
  This paper describes data collected at study entry on venous events experienced before study inclusion, i.e. the baseline data.
  
  
  METHODS
  All individuals (probands, relatives) registered in nine European thrombosis centers with the factor (F)V Leiden mutation, a deficiency of antithrombin, protein C or protein S, or a combination of these defects, were enrolled between March 1994 and September 1997. As control individuals, partners, friends or acquaintances of the thrombophilic participants were included. Incidence and relative risk of objectively confirmed venous thrombotic events (VTEs) prior to entry were calculated for the relatives with thrombophilia and the controls.
  
  
  RESULTS
  Of the 846 relatives with thrombophilia (excluding probands), 139 (16%) had experienced a VTE with an incidence of 4.4 per 1000 person years. Of the controls, 15 of the 1212 (1%) controls had experienced a VTE with an incidence of 0.3 per 1000 person years. The risk of venous thrombosis associated with familial thrombophilia was 15.7 (95% CI 9.2-26.8) and remained similar after adjustment for regional and sex-effects (16.4; 95% CI 9.6-28.0). The highest incidence per 1000 person years was found in relatives with combined defects (8.4; 95% CI 5.6-12.2), and the lowest incidence was found in those with the FV Leiden mutation (1.5; 95% CI 0.8-2.6).
  
  
  CONCLUSIONS
  Considerable differences in the lifetime risk of VTE were observed among individuals with different thrombophilia defects.
authors.affiliation: Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: C Y
authors.initials: CY
authors.lastname: Vossen
authors.forename: J
authors.initials: J
authors.lastname: Conard
authors.forename: J
authors.initials: J
authors.lastname: Fontcuberta
authors.forename: M
authors.initials: M
authors.lastname: Makris
authors.forename: F J M
authors.initials: FJ
authors.lastname: Van Der Meer
authors.forename: I
authors.initials: I
authors.lastname: Pabinger
authors.forename: G
authors.initials: G
authors.lastname: Palareti
authors.forename: F E
authors.initials: FE
authors.lastname: Preston
authors.forename: I
authors.initials: I
authors.lastname: Scharrer
authors.forename: J C
authors.initials: JC
authors.lastname: Souto
authors.forename: P
authors.initials: P
authors.lastname: Svensson
authors.forename: I D
authors.initials: ID
authors.lastname: Walker
authors.forename: F R
authors.initials: FR
authors.lastname: Rosendaal
mesh_terms: D000293:Adolescent; D000328:Adult; D015331:Cohort Studies; D005060:Europe; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors; D019851:Thrombophilia / Q000097:blood / Q000150:complications* / Q000235:genetics*; D020246:Venous Thrombosis / Q000097:blood / Q000209:etiology*