Pharmacogenetics: Looking toward the future with personalized medicine

March 14, 2018
Deanna Leingang, MS, LCGC

As healthcare costs continue to rise, there has been a push across the industry to look toward personalized medicine to provide the best possible individualized patient care with the lowest cost and fewest health complications. The concept of personalized medicine has been embraced by both providers and patients. In recent years, this has caused a boom in the utilization of pharmacogenetic testing.

Pharmacogenetics, broadly, is the study of how a person’s genes may influence their body’s response to specific drugs and medications. More specifically, the field examines how different inherited variants in genes that play a role in the metabolic pathways that process medications can influence the efficacy and risk for side effects. The field of pharmacogenetics has been around since the 1950’s, and as new information has slowly accumulated about additional gene and drug interactions, it has begun to be utilized across multiple health care specialties.

Most pharmacogenetic testing, or PGx, involves a specific type of genetic test called genotyping. As compared to other types of tests, like sequencing, which read through the entirety of a gene, genotyping tests look at specific points within the gene where we know variants are common and check for these specific changes.

Since we each inherit one copy of each of our genes from each parent, a person will have two copies of each of the genes analyzed by PGx in most cases. Each copy is called an allele. For most genes, a star (*) and number system has been used to classify different pharmacogenetic alleles. This means for each gene analyzed, a person is expected to have two results (for example, *1/*2). A PGx report will contain information about whether the allele identified is expected to metabolize a medication normally (indicating the person is an extensive metabolizer), if the allele is expected to metabolize a medication more quickly than average (ultra-rapid metabolizer), or if the allele will slow or impair the gene’s ability to metabolize a medication (poor metabolizer). A person’s genetic status, meaning which two alleles they have for a particular gene, is called their genotype.

A person’s genotype is used to predict how well a medication may work for them or whether there are risks for harmful side effects. Results from most PGx tests are broken into three categories, which are colored for ease of use. Green recommendations indicate that a medication can be prescribed as normal and a patient is not expected to have adverse reactions based on available genotype information. Yellow recommendations typically mean a medication may not work as effectively or a different dosage may be indicated. Red recommendations often mean a medication is contraindicated based on a patient’s genotype, and an alternative medication should be considered. In some cases, PGx testing will indicate a medication is not recommended, but it does not necessarily propose an alternative. The selection of alternative medications is made by the prescribing provider, combining other clinical information and history with PGx.

Not all PGx results are created equal. Some genes have been studied for an extended period of time and have strong evidence supporting their role in drug metabolism. For other genes, evidence may still be emerging. Those genes with the strongest supporting evidence will have guidelines established by the Clinical Pharmacogenetics Implementation Consortium (CPIC). Some genes will have weaker or conflicting evidence regarding their role in drug metabolism. Understanding the strength of evidence is an important aspect of interpreting and utilizing your PGx results in prescribing practice. For more detailed information about specific gene variant and drug interactions and further education about pharmacogenetics, we highly recommend visiting the PharmGKB website.

As this exciting field grows, healthcare providers and patients will be inundated with ever-changing information. Learn more about Lineagen's pharmacogenetic test here.

If you would like to speak with a Lineagen genetic counselor to discuss how PGx testing may fit into your practice, please contact our clinical team by phone at 801-931-6191 or by email at