title: The risk of recurrent venous thromboembolism in patients with an Arg506-->Gln mutation in the gene for factor V (factor V Leiden).
abstract: BACKGROUND
  A recently discovered mutation in coagulation factor V (Arg506-->Gln, referred to as factor V Leiden), which results in resistance to activated protein C, is found in approximately one fifth of patients with venous thromboembolism. However, the risk of recurrent thromboembolism in heterozygous carriers of this genetic abnormality is unknown.
  
  
  METHODS
  We searched for factor V Leiden in 251 unselected patients with a first episode of symptomatic deep-vein thrombosis diagnosed by venography. The patients were followed prospectively for a mean of 3.9 years to determine the frequency of recurrent venous thrombosis and pulmonary embolism.
  
  
  RESULTS
  Factor V Leiden was found in 41 of the patients (16.3 percent; 95 percent confidence interval, 11.8 to 20.9 percent). The cumulative incidence of recurrent venous thromboembolism after follow-up of up to eight years was 39.7 percent (95 percent confidence interval, 22.8 to 56.5 percent) among carriers of the mutation, as compared with 18.3 percent (95 percent confidence interval, 12.3 to 24.3 percent) among patients without the mutation (hazard ratio, 2.4; 95 percent confidence interval, 1.3 to 4.5; P<0.01).
  
  
  CONCLUSIONS
  The risk of recurrent thromboembolic events is significantly higher in carriers of factor V Leiden than in patients without this abnormality. Large trials assessing the risk-benefit ratio of long-term anticoagulation in carriers of the mutation who have had a first episode of venous thromboembolism are indicated.
authors.affiliation: Institute of Medical Semeiotics, University Hospital of Padua, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Simioni
authors.forename: P
authors.initials: P
authors.lastname: Prandoni
authors.forename: A W
authors.initials: AW
authors.lastname: Lensing
authors.forename: A
authors.initials: A
authors.lastname: Scudeller
authors.forename: C
authors.initials: C
authors.lastname: Sardella
authors.forename: M H
authors.initials: MH
authors.lastname: Prins
authors.forename: S
authors.initials: S
authors.lastname: Villalta
authors.forename: F
authors.initials: F
authors.lastname: Dazzi
authors.forename: A
authors.initials: A
authors.lastname: Girolami
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005165:Factor V / Q000235:genetics*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D017354:Point Mutation; D015995:Prevalence; D011486:Protein C / Q000378:metabolism; D012008:Recurrence; D012307:Risk Factors; D013924:Thrombophlebitis / Q000209:etiology / Q000235:genetics*
chemical_list: D011486:Protein C; D005165:Factor V