Standardizing CYP2D6 Genotype Testing
New recommendations from the Association of Molecular Pathology for CYP2D6 genotyping
The Association of Molecular Pathology (AMP) Pharmacogenomics (PGx) Working Group has published recommendations for alleles to be included in CYP2D6 clinical genotyping assays (1). Most clinical laboratories undertaking CYP2D6 PGx take a targeted genotyping approach; however, this presents a challenge in CYP2D6 due to its number of alleles and structural variants.
In the AMP recommendations, alleles are divided into a two-tier categorization system – those in Tier 1 are recommended to be included in all CYP2D6 genotype testing as a minimum panel; Tier 2 includes alleles that did not meet all the inclusion criteria for Tier 1 and may be included as additional alleles for testing.
The following inclusion criteria were set for Tier 1 variant alleles:
- Have a well-characterized effect on the function of the protein and/or gene expression
- Have an appreciable minor allele frequency in a population/ethnicity group
- Have publicly available reference materials
Alleles that met all three criteria were included in Tier 1. On the other hand, Tier 2 variant alleles meet at least one of the above criteria, but not all, and can be moved to Tier 1 if additional information or reference materials become available. The recommendations are meant to be a reference guide for labs, rather than restrictive rules, with the goal of promoting standardization of CYP2D6 PGx testing across labs and, in turn, improving patient care.
- VM Pratt et al., J Mol Diag, [Online ahead of print] (2021). PMID: 34118403.
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