title: ABO blood group, other risk factors and incidence of venous thromboembolism: the Longitudinal Investigation of Thromboembolism Etiology (LITE).
abstract: BACKGROUND
  Numerous case-control studies have reported higher prevalence of non-O blood type among venous thromboembolism (VTE) patients than controls, but potential mechanisms or effect modifiers for the association are not fully established.
  
  
  METHODS
  Using a nested case-control design combining the Atherosclerosis Risk in Communities and the Cardiovascular Health Study cohort, ABO blood type and other VTE risk factors were measured on pre-event blood samples of 492 participants who subsequently developed VTE and 1008 participants who remained free of VTE.
  
  
  RESULTS
  A total of 64.4% of cases and 52.5% of controls had non-O blood type. Among controls, mean values of factor VIIIc (FVIIIc) and von Willebrand factor among the non-O blood type group were higher than among the O group. Compared with O blood type, the age-adjusted odds ratio (OR) of VTE for non-O blood type was 1.64 (95% CI, 1.32-2.05) and was similar for the two parent studies and race groups. Further adjustment for sex, race, body mass index, diabetes mellitus and FVIIIc reduced the OR: 1.31 (95% CI, 1.02-1.68). Factor V Leiden (FV Leiden) appeared to modify the non-O blood type association with VTE in a supra-additive fashion, with an age-, sex- and race-adjusted OR of 6.77 (95% CI, 3.65-12.6) for having both risk factors.
  
  
  CONCLUSIONS
  Non-O blood type was independently associated with risk of VTE, and added to the risk associated with FV Leiden.
authors.affiliation: Division of Epidemiology and Community Health, University of Minnesota, Minneapolis, MN 55454-1015, USA.
authors.forename: T
authors.initials: T
authors.lastname: Ohira
authors.forename: M
authors.initials: M
authors.lastname: Cushman
authors.forename: M Y
authors.initials: MY
authors.lastname: Tsai
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.forename: S R
authors.initials: SR
authors.lastname: Heckbert
authors.forename: N A
authors.initials: NA
authors.lastname: Zakai
authors.forename: W D
authors.initials: WD
authors.lastname: Rosamond
authors.forename: A R
authors.initials: AR
authors.lastname: Folsom
mesh_terms: D000017:ABO Blood-Group System; D000368:Aged; D016022:Case-Control Studies; D048909:Diabetes Complications / Q000097:blood / Q000209:etiology; D005165:Factor V / Q000378:metabolism; D005169:Factor VIII / Q000378:metabolism; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D013923:Thromboembolism / Q000097:blood* / Q000209:etiology*; D020246:Venous Thrombosis / Q000097:blood* / Q000209:etiology*; D014841:von Willebrand Factor / Q000378:metabolism
chemical_list: D000017:ABO Blood-Group System; C095381:factor V Leiden; D014841:von Willebrand Factor; D005165:Factor V; D005169:Factor VIII