Interpretation and Reporting of Results

Interpretation and reporting is the step that turns raw genetic data into a clinically usable statement. Detected alleles are named, combined into a diplotype, and translated into a predicted phenotype such as a metabolizer category; that phenotype is then communicated in a report using standardized terms. Because inconsistent wording once made pharmacogenomic reports hard to compare and act on, consensus terminology and translation rules are central to this topic.

Definition

Interpretation and reporting of pharmacogenomic results is the process of converting detected alleles into a diplotype and a predicted drug-response phenotype, then communicating that phenotype in a clinical report using standardized, consensus-based terminology.

Scope

This entry covers genotype-to-phenotype translation, the standardized phenotype categories used to describe drug response, the consensus terminology for clinical pharmacogenetic results, and why standardization matters for clarity across laboratories and decision-support systems. It uses CYP2D6 translation as an illustrative case of the complexity involved. It is a reference description of interpretation and reporting practice, not a guide to acting on any specific result.

Core questions

• How is a genotype translated into a predicted phenotype?
• What standardized terms describe drug-response phenotypes, and why were they agreed?
• Why is consistent terminology important across laboratories and systems?
• What makes translation for genes like CYP2D6 especially complex?

Key concepts

• Diplotype assembly
• Genotype-to-phenotype translation
• Metabolizer phenotype categories
• Standardized result terminology
• Activity scores for complex genes
• Report clarity and comparability

Mechanisms

After a laboratory detects variants, the alleles are named using star-allele nomenclature and combined into a diplotype (Gaedigk et al., 2017). The diplotype is mapped to a predicted phenotype, often expressed as a metabolizer category, using consensus translation rules; for complex genes such as CYP2D6 an activity-score approach sums the functional contributions of each allele before assigning a phenotype (Caudle et al., 2019). The predicted phenotype is then reported using standardized terms agreed by consortia so that the same genotype yields the same descriptive language regardless of laboratory (Caudle et al., 2017). Standardized terminology and translation rules allow downstream decision-support systems to interpret reports consistently and reduce ambiguity for clinicians (Roden, 2019).

Clinical relevance

Clear, standardized interpretation lets readers understand what a pharmacogenomic report is asserting about predicted drug response and how confidently. Appreciating how a genotype becomes a reported phenotype is part of appraising such reports. This entry explains the reporting process and terminology; it does not interpret any individual result or translate a phenotype into a prescribing or dosing decision.

Evidence & guidelines

Consensus terminology for clinical pharmacogenetic test results was established by the Clinical Pharmacogenetics Implementation Consortium to harmonize how phenotypes are reported (Caudle et al., 2017), and joint CPIC and Dutch Pharmacogenetics Working Group recommendations standardized genotype-to-phenotype translation for CYP2D6 (Caudle et al., 2019). Allele definitions underpinning these translations are curated by the Pharmacogene Variation Consortium (Gaedigk et al., 2017). These are standardization frameworks, not individualized clinical advice.

History

Early pharmacogenomic reports varied widely in how they described phenotypes, which hampered comparison and decision support. To address this, the Clinical Pharmacogenetics Implementation Consortium published consensus terms for clinical pharmacogenetic test results in 2017 (Caudle et al., 2017), and a joint effort with the Dutch Pharmacogenetics Working Group later standardized translation for the difficult CYP2D6 gene (Caudle et al., 2019). These efforts, built on consortium-curated allele nomenclature (Gaedigk et al., 2017), made reporting more uniform across the field.

Debates

Standardizing phenotype categories for complex genes

Assigning a single phenotype to highly variable genes such as CYP2D6 is difficult, and consensus on activity-score thresholds and phenotype boundaries required explicit harmonization between major frameworks.

Key figures

• Kelly E. Caudle
• Andrea Gaedigk
• Michelle Whirl-Carrillo
• James M. Hoffman

Seminal works

• caudle-2017
• caudle-2019
• gaedigk-2017

Frequently asked questions

What is a metabolizer phenotype?

It is a predicted category describing how a person is expected to process certain drugs based on their genotype, such as poor, intermediate, normal, or ultrarapid metabolizer; it is a prediction derived from the genetic result, not a direct measurement of drug levels.

Why does standardized terminology matter?

Consistent terms ensure that the same genotype is described the same way across laboratories and decision-support systems, reducing ambiguity and making reports easier to compare and act on appropriately.