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VKORC1 polymorphisms, haplotypes and haplotype groups on warfarin dose among African-Americans and European-Americans.

BACKGROUND: Although the influence of VKORC1 and CYP2C9 polymorphisms on warfarin response has been studied, variability in dose explained by CYP2C9 and VKORC1 is lower among African-Americans compared with European-Americans. This has lead investigators to hypothesize that assessment of VKORC1 haplotypes may help capture a greater proportion of the variability in dose for this under-represented group. However, the inadequate representation of African-Americans and the assessment of a few VKORC1 polymorphisms have hindered this effort. METHODS: To determine if VKORC1 haplotypes or haplotype groups explain a higher variability in warfarin dose, we comprehensively assessed VKORC1 polymorphisms in 273 African-Americans and 302 European-Americans. The influence of VKORC1 polymorphisms, race-specific haplotypes and haplotype groups on warfarin dose was evaluated in race-stratified multivariable analyses after accounting for CYP2C9 (*2, *3, *5, *6 and *11) and clinical covariates. RESULTS: VKORC1 explained 18% (30% with CYP2C9) variability in warfarin dose among European-Americans and 5% (8% with CYP2C9) among African-Americans. Four common haplotypes in European-Americans and twelve in African-Americans were identified. In each race VKORC1 haplotypes emerged into two groups: low-dose (Group A) and high-dose (Group B). African-Americans had a lower frequency of Group A haplotype (10.6%) compared with European-Americans (35%, p < 0.0001).The variability in dose explained by VKORC1 haplotype or haplotype groups was similar to that of a single informative polymorphism. CONCLUSIONS: Our findings support the use of CYP2C9, VKORC1 polymorphisms (rs9934438 or rs9923231) and clinical covariates to predict warfarin dose in both African- and European-Americans. A uniform set of common polymorphisms in CYP2C9 and VKORC1, and limited clinical covariates can be used to improve warfarin dose prediction for a racially diverse population.

Pubmed ID: 18855533

Authors

  • Limdi NA
  • Beasley TM
  • Crowley MR
  • Goldstein JA
  • Rieder MJ
  • Flockhart DA
  • Arnett DK
  • Acton RT
  • Liu N

Journal

Pharmacogenomics

Publication Data

October 15, 2008

Associated Grants

  • Agency: NINDS NIH HHS, Id: K23 NS045598
  • Agency: NINDS NIH HHS, Id: K23 NS045598-05
  • Agency: NINDS NIH HHS, Id: K23NS45598-01

Mesh Terms

  • Adult
  • African Americans
  • Aged
  • Anticoagulants
  • Cohort Studies
  • European Continental Ancestry Group
  • Female
  • Forecasting
  • Haplotypes
  • Humans
  • Male
  • Middle Aged
  • Mixed Function Oxygenases
  • Polymorphism, Genetic
  • Vitamin K Epoxide Reductases
  • Warfarin