Clinical Pharmacogenetics: Results After Implementation of Preemptive Tests in Daily Routine

Background/Objectives: The clinical implementation of pharmacogenetics (PGx) remains limited, even for well-established drug-gene interactions. In addition to insufficient infrastructure and PGx education among healthcare professionals, there is currently no consensus regarding which genetic variants should be tested, the most appropriate testing approach (e.g., single-gene vs. multi-gene panels), or how to translate genotypes into actionable therapeutic recommendations. Methods: We describe the implementation of PGx in real daily clinical routine at a single institution to guide other centers. We analyze the drug-gene interactions and genetic variants included in our program based on allelic, genotypic, and phenotypic frequencies, resulting therapeutic recommendations. Linkage disequilibrium and haplotype analyses are also performed. Results and Conclusions: PGx testing was primarily requested by the oncology department. Not all variants included in typical panels had clinical utility in our setting. We do not recommend testing CYP2C19*17 prior to clopidogrel prescription, as it does not translate into a dosing recommendation. TPMT*3B may be considered just to confirm TPMT*3A due to its linkage with TPMT*3C. Similarly, we do not recommend the routine testing of CYP2C9*2 prior to siponimod prescription, as it does not inform therapeutic decisions according to the current drug label.