title: Elevated factor IX activity is associated with an increased odds ratio for both arterial and venous thrombotic events.
abstract: OBJECTIVE
  Elevations of factor IX (FIX) are thought to contribute to thrombotic risk, but this has not been well characterized. We retrospectively sought to determine whether elevated FIX levels are a risk factor for thrombosis in 81 adult subjects younger than 65 years (mean, 47 years) who were referred for evaluation of a hypercoagulable state.
  
  
  METHODS
  Patients were classified by arterial transient ischemic attack/stroke (TIA/stroke, n = 62) or venous thromboembolism (VTE, n = 19) events. FIX activity testing was performed on all 81 subjects and a reference group of 40 healthy individuals.
  
  
  RESULTS
  Thirteen (21%) of 62 subjects with TIA/stroke and 5 (26%) of 19 subjects with VTE had elevated FIX activity. Odds ratios for TIA/stroke and VTE in subjects with elevated FIX activity were 3.7 (95% confidence interval [CI], 0.76-17.65) and 6.8 (95% CI, 1.18-39.07), respectively.
  
  
  CONCLUSIONS
  Our findings suggest an association between elevated FIX levels and both arterial and venous thrombotic events.
authors.affiliation: ARUP Laboratories, 500 Chipeta Way, Mail Stop 115-G04, Salt Lake City, UT 84108; kristi.smock@aruplab.com.
authors.forename: Nahla M
authors.initials: NM
authors.lastname: Heikal
authors.forename: Karla K
authors.initials: KK
authors.lastname: Murphy
authors.forename: Ronda A
authors.initials: RA
authors.lastname: Crist
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Wilson
authors.forename: George M
authors.initials: GM
authors.lastname: Rodgers
authors.forename: Kristi J
authors.initials: KJ
authors.lastname: Smock
mesh_terms: D000328:Adult; D002536:Cerebral Arteries / Q000378:metabolism / Q000473:pathology*; D005164:Factor IX / Q000378:metabolism*; D005260:Female; D006801:Humans; D002546:Ischemic Attack, Transient / Q000453:epidemiology / Q000378:metabolism / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D012189:Retrospective Studies; D012307:Risk Factors; D014589:Utah / Q000453:epidemiology; D054556:Venous Thromboembolism / Q000453:epidemiology / Q000378:metabolism / Q000473:pathology; D055815:Young Adult
chemical_list: D005164:Factor IX
keywords: Arterial thrombosis; Factor IX; Stroke; Venous thrombosis