In an era where personalized healthcare solutions are gaining prominence, the role of pharmacogenetic testing cannot be understated. It offers a unique avenue to optimize medication selection and dosage for individuals, ensuring more effective and safer treatment.

In this article, we aim to shed light on the world of pharmacogenetic testing, a groundbreaking approach that allows for tailored treatment decisions based on an individual's genetic makeup. As pharmacogenetic testing becomes more prominent, it is crucial to understand its principles, benefits, and limitations, as pharmacogenetic testing can be pivotal in making informed choices regarding your healthcare.

Whether you are a patient striving to optimize your treatment or a healthcare professional seeking to enhance patient care, this comprehensive guide will equip you with key insights into pharmacogenetic testing.

What Is Pharmacogenetic Testing?

Pharmacogenetics can be broken down most simply as the study of how our genetics influence the way our bodies respond to medications. Our genes can define the way treatments are absorbed into the body, travel where they are needed within the body, and ultimately, how these medications are removed after having their effect. These processes guide how well a medication works and how likely it may be to cause side effects.

Pharmacogenomic research has identified specific genes that influence these processes within the body. Pharmacogenetic testing, or PGx tests, can be used to predict gene-based responses to medications. This opens up the opportunity for more individually tailored therapy by taking a test to see what medications may be more likely to work for you.

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Personalized Medicine

Much of the research and guidelines focus on the way medications are metabolized or processed within the body. Genetic testing for drug metabolism can provide some fundamental insights into whether medications are likely to be metabolized:

  • More quickly, rendering a drug less effective.
  • Less quickly, allowing a drug to build up and increase the risk of side effects.

There are also established associations between genes like HLA-B and the potential for severe hypersensitivity or allergic reactions like Stevens-Johnson Syndrome. In this instance, awareness of these risks can provide more informed decisions related to medications like carbamazepine or phenytoin.

Traditionally, population-based statistics are used to make treatment decisions, and many adjustments are made after therapy has already started. Identifying genetic differences among individuals allows a prescribing healthcare professional to make finer adjustments before an initial prescription is written. Dosing may be better targeted, or alternative medications can be selected based on likely responses.

Types of Pharmacogenetic Testing

A majority of existing genetic tests focus on the cytochrome P450 or CYP enzyme system. These genes are primarily expressed in the liver and are ultimately responsible for roughly half of the elimination of common medications. Many drug interactions are defined by the CYP system, with some medications increasing or decreasing the metabolism of other circulating drugs. Genetic testing helps predict the baseline metabolism of individual components of the CYP system.

DNA tests for medication metabolism cover some of the enzymes that are most commonly involved in the processing of medications:

  • CYP1AC.
  • CYP2C19.
  • CYP2C9.
  • CYP2D6.

There are also a number of other specific genes like HLA, DPYD, or TPMT that predict a higher likelihood of potentially severe reactions.

Testing for MTHFR allows for tailored therapy for patients who may be at risk for developing active folate imbalances. Active folate is crucial in many processes within the body. Deficiencies raise the risk for health concerns ranging from cancer to major depression. Detecting an MTHFR variability allows prescribers to place a focus on folate and the medications that may impact it, improving patient care.

In practice, pharmacogenetic testing has been adopted most prominently in psychiatry. While the benefits for patients managing mental health have been an early focus, there is significant potential for improved therapy in many areas. Research continues to provide additional insights, and tests are available that cover medications used in managing many different conditions, including:

  • ADHD.
  • Depression.
  • Anxiety.
  • Bipolar disorder.
  • Schizophrenia.
  • Opioid withdrawal.
  • Pain management.
  • HIV.
  • Diabetes.
  • Dementia.
  • Alzheimer’s.
  • Seizures.
  • Rheumatology.
    FDA approval of clinical recommendations based on results are published based on specific gene-drug interactions. The facilities used to process samples and provide results are CLIA-certified and COLA-accredited.

How does pharmacogenetic testing work?

A pharmacogenetic test can be ordered by a physician or requested by a patient directly. The results can be sent directly to a clinic or sent to a patient to review with a healthcare provider at their leisure. Ultimately, the results are used to supplement conversation with a provider if prescription therapy is being considered and will factor into an overall analysis of patient needs, risks, and benefits.

At ClarityX, there are two basic genetic testing options, each involving a simple mouth swab. Mindwell offers results focused on mental health conditions, while Max Rx extends results to over 210 medications for a variety of therapeutic areas.

DNA Sample Collection

A cheek swab genetic test can be performed at home. Materials are provided along with prepaid packaging to prepare the swab for safe shipping to the lab. Once the sample is received, it generally takes about seven to ten business days for DNA extraction, analysis, and identification of genetic variants.

Privacy is paramount; genetic data isn’t stored for any purposes other than the necessary information needed to generate your requested report. An independent physician reviews your request, and a clinical pharmacist certified in pharmacogenetics assists with interpreting the results, including discussion with your local provider if you wish.

Who Does Pharmacogenetic Testing?

While many individuals may choose to undergo testing in response to a specific diagnosis or while considering specific medications, this isn’t a requirement. Genetic testing can be performed prior to a direct need for medication, and results can be retained for future reference. This may aid in decision-making in the future, depending on developing needs.

From a clinical standpoint, psychiatrists have more actively implemented the practice in recent years. There is mounting evidence suggesting a benefit for more implementation within other areas of practice, including primary care settings, however. Because of the assumed increasing availability of individual genetic data, many clinical practice guidelines focus on the interpretation of results rather than procedures surrounding ordering the tests.

How Accurate Is Pharmacogenetic Testing

Genetic testing is generally highly accurate, but there are some potential areas that can affect results. Some of these include:

  • The DNA sample size is too small: If there’s simply not enough DNA collected, the analysis may be incomplete or inaccurate.
  • Contamination of the sample: Directions should be followed carefully while obtaining the sample to minimize the risk of contamination. The lab will also take necessary precautions to process the sample in a sterile environment.
  • Improper storage or handling: Directions should also be followed carefully to ensure the sample is properly prepared for shipment to the lab. Upon arrival, the lab takes necessary precautions to avoid sample degradation.
  • Interpretation of results: Genetic information is valuable, but open communication regarding your health status and health history is also crucial in the final decision-making process regarding therapy.

At-home tests use cheek swabs, which are noninvasive and simple to collect. Following the included instructions is crucial for ensuring accurate results, however. If additional support is needed during any portion of the testing process, live help is available.

Benefits of pharmacogenetic testing

From an individual’s perspective, the potential for frustration with a “wait and see” approach to healthcare is considerable. You may feel as though you are taking an active role in your healthcare, and ultimately you find yourself spending months or even years going through trials of medications and reporting on their effects. Aside from the potential for lost time and increased financial burden, there are also very real risks of side effects throughout this process.

Managing mental health is a prime example of some of these challenges. Unfortunately, there is a relatively high rate of treatment failure or incomplete remission of symptoms related to conditions like depression.

At-home pharmacogenetic testing offers a simplified approach with the potential to bypass some of this guesswork. As you learn more about your genetic makeup, you also learn which therapies may be more effective and which should be avoided. This has the potential to translate into more time spent treating your conditions effectively and less time bouncing back and forth between the clinic and pharmacy trying the next medication in line. Depending on the potential severity of side effects (or the impact of ineffective treatment), it may also translate into avoiding trips to the emergency room.

Clinical Studies

From a broader clinical perspective, we do see some of these effects taking shape in research data. In a recent systematic review of multiple studies focusing on pharmacogenetic testing in targeted populations (i.e., nursing homes, hospital in-patients, etc.), it was found that intervention resulted in:

  • Identification of drug-gene interactions in as many as 78% of participants.
  • Reduced hospitalization rates of 40%--52%.
  • Reduced emergency department visits of 42%--70%.
  • Estimated cost savings as high as $4,382 per patient over an 8-week follow-up using Medicare all-cause readmission and emergency department cost estimates.

Studies have shown that actionable drug-gene pairs are fairly ubiquitous, with pre-emptive testing finding actionable variants in as many as 90% or more of patients. In a study involving nearly 53,000 medical home residents, an estimated 400 adverse drug events could have been prevented over the course of a 5-year period. Across a broader population of patients who take five or more medications, testing results in an estimated $621 average annual savings.

These studies also highlight some of the current shortcomings of clinical research, however. Randomized controlled trials are fairly sparse and often include small sample sizes, for instance. The current evidence is promising, but further research would provide clearer insight into the broader impact of genetic testing for optimizing drug therapy.

Limitations of pharmacogenetic testing and hope for the future

In many respects, genetic testing for medications is still in its infancy. Pharmacogenetics is an expanding field with tremendous potential, but there are some limitations to be aware of:

  • There is more reliable evidence for some medications compared with others.
  • Many medications have no actionable data available related to genetic influence.
  • Insurance coverage is minimal most insurers deny claims causing patients to have high our of pocket costs.

The economic impact of gene testing is promising, but further research is likely to be beneficial before consistent, widespread insurance coverage is available.

While not necessarily a limitation of genetic testing itself, it’s important to keep in mind that it’s one piece of a larger puzzle. Your doctor will be able to incorporate this information while helping you decide which treatment options will be best for you.

There is also the consideration of pharmacogenetics vs. pharmacogenomics. Pharmacogenetic tests provide us with information about individual genes, but in many ways, this can be considered the tip of the iceberg. Pharmacogenomics research seeks to “zoom out” and give us a more complete picture of the delicate dance between genes across the genome — and the epigenetic factors that influence their expression.

There is a good foundation of knowledge to build on, and we can already make helpful decisions based on gene testing. As time goes on, there will be opportunities to learn more about the effects of additional genes, epigenetic effects, and a wider variety of medications covering more health concerns.

In the years to come, personalized medicine is in fact to become a standard of care.

Looking for help understanding the right treatment option for your specific concern? Genetic testing may help you save time searching for effective therapy, avoid harmful side effects, and provide further valuable insight that may help you address future needs. See how ClarityX can help!