Genetic determinants of variability in warfarin response after the dose-titration phase.

Iwuchukwu OF, Ramirez AH, Shi Y, Bowton EA, Kawai VK, Schildcrout JS, Roden DM, Denny JC, Stein CM
Pharmacogenet Genomics. 2016 26 (11): 510-516

PMID: 27632229 · PMCID: PMC5300764 · DOI:10.1097/FPC.0000000000000244

OBJECTIVES - Genetic factors contribute considerably toward variability in warfarin dose requirements and are important in the dose-titration phase; their effects on the stability of anticoagulation later in therapy are not known.

METHODS - Using deidentified electronic medical records linked to a DNA-biobank, we studied 140 African-Americans and 943 European-Americans after the warfarin dose-titration phase. We genotyped 12 single nucleotide polymorphisms in genes (CYP2C9, VKORC1, CYP4F2, GGCX, EPHX1, CALU) associated with altered warfarin dose requirements and tested their associations with international normalized ratio variability (INRVAR) and percent time in therapeutic range in European-Americans and African-Americans.

RESULTS - One allele copy of rs2108622 in CYP4F2 was associated with a 15% [95% confidence interval (CI): 1-26, P=0.03] decrease in the median INRVAR in European-Americans. In African-Americans, GGCX variants rs11676382 and rs699664 were associated with 4.16-fold (95% CI: 1.45-11.97, P=0.009) and 1.50-fold (95% CI: 1.07-2.08, P=0.02) changes in the median INRVAR per variant allele copy, respectively; rs11676382 was also significantly associated with a 23.19% (95% CI: 5.89-40.48, P=0.01) decrease in time in therapeutic range. The total variation in INRVAR explained by both clinical factors and rs2108622 was 5.2% for European-Americans. In African-Americans, the inclusion of GGCX variants rs11676382 and rs699664, and the CYP2C9*8 variant rs7900194 explained ∼29% of the variation in INRVAR.

CONCLUSION - The stability of anticoagulation after the warfarin dose-titration phase is differentially affected by variants in CYP4F2 in European-Americans and GGCX loci in African-Americans.

MeSH Terms (19)

Adult African Americans Aged Aged, 80 and over Anticoagulants Calcium-Binding Proteins Carbon-Carbon Ligases Cytochrome P-450 CYP2C9 Cytochrome P450 Family 4 Epoxide Hydrolases European Continental Ancestry Group Female Humans International Normalized Ratio Male Middle Aged Pharmacogenomic Variants Vitamin K Epoxide Reductases Warfarin

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