title: The factor VR506Q mutation causing APC resistance is highly prevalent amongst unselected outpatients with clinically suspected deep venous thrombosis.
abstract: OBJECTIVE
  Resistance to activated protein C (APC resistance), caused by a single point mutation in the factor V gene (FV:R506Q), is a major risk factor for venous thrombosis. As the significance of this mutation among unselected outpatients with deep-vein thrombosis (DVT) is not established, we have studied its prevalence among consecutive outpatients attending the emergency room due to a clinically suspected DVT.
  
  
  METHODS
  The FV:R506Q mutation was determined in 223 consecutive Swedish outpatients with clinically suspected DVT, and in 288 healthy controls. Using phlebography, the patients were classified as DVT-positive or DVT-negative.
  
  
  METHODS
  The prevalence of FV:R506Q mutation.
  
  
  RESULTS
  The prevalence of the FV:R506Q mutation was 28% (28/99) in the DVT-positive subgroup (relative risk: 3.1; 95% CI: 1.7-5.5), and 23% (28/124) in the DVT negative subgroup (relative risk: 2.0; 95% CI: 1.1-3.6), as compared to 11% (32/288) in the control group. In the DVT-positive subgroup, the FV:R506Q mutation was most common among younger patients with primary thrombosis (47%) and least common among older patients with secondary thrombosis (19%). The high prevalence of FV:R506Q mutation among DVT-negative patients was associated with a high frequency of previous venous thrombosis. Thus, 46% (13/28) of the DVT-negative FV:R506Q carriers had a history of thrombosis, compared with only 22% (21/96) of the DVT-negative patients lacking the mutation (P = 0.01).
  
  
  CONCLUSIONS
  To sum up, the FV:R506Q mutation is present in more than a quarter of Swedish DVT-positive outpatients with clinically suspected DVT, indicating that APC-resistance is a major thrombotic risk factor contributing to the high incidence of venous thrombosis in Sweden.
authors.affiliation: Department of Coagulation Disorders, University of Lund, University Hospital, Malmö, Sweden.
authors.forename: P J
authors.initials: PJ
authors.lastname: Svensson
authors.forename: B
authors.initials: B
authors.lastname: Zöller
authors.forename: I
authors.initials: I
authors.lastname: Mattiasson
authors.forename: B
authors.initials: B
authors.lastname: Dahlbäck
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D005165:Factor V / Q000235:genetics*; D015943:Factor Va / Q000235:genetics*; D005260:Female; D006580:Genetic Carrier Screening; D006801:Humans; D008297:Male; D008875:Middle Aged; D010045:Outpatients; D010690:Phlebography; D017354:Point Mutation / Q000235:genetics*; D015995:Prevalence; D011486:Protein C / Q000235:genetics*; D013924:Thrombophlebitis / Q000000981:diagnostic imaging / Q000235:genetics*
chemical_list: D011486:Protein C; C095381:factor V Leiden; D015943:Factor Va; D005165:Factor V