Background: Interindividual differences in CYP2D6 activity range from total absence of metabolism of certain drugs to ultrafast metabolism and can produce adverse effects or lack of therapeutic effect under standard therapy. Several mutations have been described in the CYP2D6 gene that abolish CYP2D6 activity. However, four mutations explain the majority of the poor metabolizers. We describe four single-tube assays to detect these mutations.
Methods: Three tetra-primer PCR assays were developed to detect the mutations in the CYP2D6*3, *4, and *6 alleles. In these single-tube assays, the CYP2D6 locus is amplified directly, followed by the allele-specific amplification on this new template. In addition, a multiplex long PCR was developed to genotype the CYP2D6*5 allele. Two long PCR amplifications for detection of the deletion of CYP2D6 (*5) and for detection of the CYP2D6 gene region were combined in one tube.
Results: Analysis of 114 alleles showed no CYP2D6*3 allele, and allele frequencies of 28.1% for CYP2D6*4, 2.6% for CYP2D6*5, and 0. 9% for CYP2D6*6. Re-analysis of the DNA samples by restriction fragment length polymorphism and sequencing analysis confirmed these results. Furthermore, re-analysis of sequenced genomic DNA by tetra-primer PCR analysis (7-11 times) always showed identical results.
Conclusions: Our set of single-tube assays allows rapid and reproducible genotyping of the majority of CYP2D6 poor metabolizers.