Clinical Application of Pharmacogenetics: Where are We Now?

Pharmacogenetic (PGx) testing has the potential to improve drug therapy in an individual by informing appropriate drug dosing or drug selection in order to maximize efficacy and safety. Although multiple studies have illustrated the potential benefits of such testing when applied to specific drugs across a broad range of therapy areas, the uptake of PGx testing in routine clinical practice has been relatively limited. Implementation appears to be hampered by the absence of sufficiently strong evidence linking the results of testing with actionable benefits in terms of clinical outcomes. Meanwhile, there are now adequate data to allow dosing recommendations as have been developed by bodies including the Dutch Pharmacogenetics Working Group (DPWG) and the Clinical Pharmacogenetics Implementation Consortium (CPIC) in several settings, including TPMT/thiopurines, CYP2C19/clopidogrel, CYP2D6/codeine, VKORC1-CYP2C9/warfarin, HLA-B*5701/abacavir, SLCO1B1/simvastatin and HLAB*5801/allopurinol. The International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) and the International Association of Therapeutic Drug Monitoring and Clinical Toxicology (IATDMCT) have also recently initiated surveys in order to better understand the extent of, and the role played by, PGx testing in clinical practice. This should help identify where further training and education may be beneficial. To this end, in collaboration with ESPT, the IFCC Pharmacogenetic Laboratory Network has now been formed, with the aim of improving the uptake and quality of PGx testing.