Reinterpretation of pharmacogenomic phenotypes after combinatorial psychiatric testing

Providers can use combinatorial pharmacogenomic panels to aid psychiatric medication prescribing. Results are typically documented in static documents which list the genotype and predicted phenotype (interpretation). However, genotype-to-phenotype translations can differ between laboratories and change as scientific consensuses evolves. Here, we describe the implications of reinterpreting phenotype after combinatorial psychiatric pharmacogenomic testing in a real-world setting.

143 patients underwent testing from 2014 to 2021. Reported genotypes and phenotypes were compared to 2024 Clinical Pharmacogenetics Implementation Consortium definitions. Chi-square tests and logistic regression were used to examine the differences in phenotype frequencies before and after reinterpretation and examine the association with time since testing.

Eighty-one patients (57%) required at least one updated interpretation. CYP2C19 interpretations changed for 44/143 patients (31%), followed by CYP2D6 (29%), CYP2B6 (3%), and CYP2C9 (1%). Reinterpretation reduced the number of CYP2D6 ultrarapid and poor metabolizers (p = 0.005), which has implications for antidepressant prescribing. Likelihood of a patient having a reinterpreted phenotype was not associated with time since reporting (p = 0.71).

Reported phenotypes from combinatorial PGx testing often do not align with current standardized definitions, even from tests performed recently. Health systems should establish procedures to standardize and periodically update pharmacogenomic interpretations.