What do we need to transfer pharmacogenetics findings into the clinic?
Recently, a portable USB compatible handheld DNA sequencer became commercially available to genotype individuals without need of a laboratory. However, does the rise of point-of-care testing imply that we are ready to implement pharmacogenetics into daily practice? Pharmacogenetics can help in defining optimal drug dosage, identifying patients at risk of drug-induced toxicity or adverse drug effects and predicting whether a prescribed drug will be effective.
In an ideal world, individual genetic information should be integrated in computer provider order entry (CPOE) systems and/or clinical decision support tools to calculate precise dosing regimens or to establish effectivity or risks of treatment before physicians generate electronic prescriptions. But what do we need to reach this stage?
First, evidence is key in implementation of pharmacogenetics testing in clinical practice, yet one can argue how much evidence is ‘enough’ to convince stakeholders. According to the clinical evidence pyramid, most weight is given to randomized controlled trials (RCTs) that compare pharmacogenetic-guided treatment strategy to usual care. However, these trials are often expensive and not always feasible to perform due to small patient populations in certain diseases. Furthermore, an RCT can even be considered unethical.
For example, in case of strong observational evidence of genetic variants associated with life-threatening drug-induced toxicities, such as CYP2D6 genotype of breastfeeding mothers and codeine-induced neonate mortality. Thus, it is important to reach consensus what level of evidence is needed to change clinical practice when precision medicine RCTs are not feasible or ethical. In our opinion strong observational evidence should be sufficient in some cases, when further randomized studies are deemed not feasible and/or ethical.