Comparison of two CYP2D6 genotyping methods and assessment of genotype-phenotype relationships.
BACKGROUND
There have been no published reports comparing the CYP450 GeneChip microarray assay with more standard methods of genetic testing.


METHODS
We collected 20-mL blood samples from 236 volunteers for DNA isolation and testing before each individual ingested 60 mg of dextromethorphan, and collected their urine. CYP2D6 alleles *3 to *7, *9, *17, and *41, and multiple CYP2D6 gene copies were tested by allele-specific PCR (AS-PCR), whereas alleles *2 to *4 and *6 to *11 were tested by the Affymetrix CYP450 GeneChip assay. Five of the CYP2D6 alleles (*3, *4, *6, *7, and *9) were tested by both AS-PCR and the CYP450 GeneChip assay in an independent and blinded fashion in 232 of the 236 healthy volunteers. The combined CYP2D6 genotype from both methods was used to divide the population into four subgroups, poor metabolizers (PMs), intermediate metabolizers (IMs), extensive metabolizers (EMs), and ultrarapid metabolizers (UMs), based on their relative function and ability to express the CYP2D6 gene. The urinary elimination of dextromethorphan was assessed in each of these CYP2D6 subgroups.


RESULTS
The CYP2D6*3, *4, *6, *7, and *9 alleles showed a high degree of concordance between the CYP450 GeneChip and AS-PCR methods (>99% concordance). The mean (SD) of the log[dextromethorphan metabolic ratio (MR)] in the four CYP2D6 subgroups was PM = 0.49 (0.38); IM = -1.24 (0.53); EM = -2.35 (0.61); and UM = -2.43 (0.38).


CONCLUSIONS
Oligonucleotide microarray technology is an efficient and reliable way to test for CYP2D6 gene variation based on five alleles compared by separate methods. The methodology is influenced by the quality and amount of DNA present. The log(dextromethorphan MR) is a highly variable index that appears to reflect the crude nature of the dextromethorphan MR as an indicator of CYP2D6 in vivo enzyme activity.
Chou
Wen-Hwei
WH
Division of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky and UK Mental Health Research Center at Eastern State Hospital, Lexington 40536, USA.
Yan
Feng-Xiang
FX
Robbins-Weilert
Doris K
DK
Ryder
Thomas B
TB
Liu
Wei Wei
WW
Perbost
Clotilde
C
Fairchild
Maureen
M
de Leon
Jose
J
Koch
Walter H
WH
Wedlund
Peter J
PJ
D019389:Cytochrome P-450 CYP2D6 / Q000097:blood / Q000235:genetics*; D003915:Dextromethorphan / Q000652:urine; D005838:Genotype; D006801:Humans; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods; D010641:Phenotype; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic
D003915:Dextromethorphan; D019389:Cytochrome P-450 CYP2D6