Robust CYP2D6 genotype assay including copy number variation using multiplex single-base extension for Asian populations.

We developed a CYP2D6 genotyping method that includes copy number variation (CNV) and recently known functional haplotypes using multiplex single-base extension (SBE). Twelve CYP2D6 alleles (*1, *2, *5, *10, *14, *18, *21, *41, *49, *52, *60, and a duplication of CYP2D6) were genotyped using 2 PCR reactions followed by multiplex SBE with 10 primers and singleplex SBE with 1 primer. The result from 758 Korean samples was validated by comparison with the results of direct sequencing or other genotyping methods. We also genotyped 89 Chinese and 122 Vietnamese subjects to determine the presence of recently identified functional alleles. All 12 CYP2D6 alleles, including gene deletion and duplication, were obviously discriminated. The concordance rate was 100% between our method and other methods. Our method also covered over 98% of the CYP2D6 genotypes in Japanese and Chinese subjects based on reported data. In addition to published genotypes, *14, *21, *41, *49, and *52 were found in about 5% in Chinese and Vietnamese. The CYP2D6 genotyping method may be clinically applicable for Asian populations. The method can be improved easily to cover other ethnic groups by utilizing additional haplotype tagging SNPs.