Selected research from leading health care experts whose findings have a direct bearing on public policies effecting medical progress. Research is chosen based on its quality and relevance by the Medical Progress Today editorial staff.

Selected Research

Effect of VKORC1 Haplotypes on Transcriptional Regulation and Warfarin Dose
Mark J. Rieder, Ph.D., Alexander P. Reiner, New England Journal of Medicine, 6-2-05

This study documents how the researchers (mentioned above) identified the genetic variation that appears to be responsible for how warfarin is metabolized differently in different patients (and even different ethnic groups). Researchers

…conducted a retrospective study of European-American patients receiving long-term warfarin maintenance therapy. Multiple linear-regression analysis was used to determine the effect of VKORC1 haplotypes on the warfarin dose. We determined VKORC1 haplotype frequencies in African-American, European-American, and Asian-American populations and VKORC1 messenger RNA (mRNA) expression in human liver samples.
We identified 10 common noncoding VKORC1 single-nucleotide polymorphisms and inferred five major haplotypes. We identified a low-dose haplotype group (A) and a high-dose haplotype group (B). The mean (±SE) maintenance dose of warfarin differed significantly among the three haplotype group combinations…
VKORC1 haplotype groups A and B explained approximately 25 percent of the variance in dose. Asian Americans had a higher proportion of group A haplotypes and African Americans a higher proportion of group B haplotypes. VKORC1 mRNA levels varied according to the haplotype combination.
The management of warfarin therapy is complicated by a wide variation among patients in drug response. Variants in the gene encoding vitamin K epoxide reductase complex 1 (VKORC1) may affect the response to warfarin…. VKORC1 haplotypes can be used to stratify patients into low-, intermediate-, and high-dose warfarin groups and may explain differences in dose requirements among patients of different ancestries.

Project FDA.
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