Potential Clinical Impact of Testing for Higher Threshold of CYP2D6 Copy Number Variation

September 28, 2026

Introduction

  • CYP2D6 is one of the most clinically important pharmacogenes, but also one of the most polymorphic.
    • CYP2D6 can have copy number variation (CNV), which can be impactful to function and predicted phenotype.
  • Association for Molecular Pathology joint consensus recommendation includes guidance for testing CYP2D6 CNVs but does not specify the number of copies to test for.
  • Purpose of this analysis was to determine how often distinguishing three versus four CYP2D6 copies would be clinically impactful.