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Pharmacogenetic Testing

Personalized medicine through genetic testing

Historically, medication has been prescribed with a “one-size-fits-all” approach. Advances in genetic testing now allow medication to be tailored to the individual. In 2003 the Human Genome Project mapped the entire human genome (the complete set of DNA). Humans have 23 pairs of chromosomes within the nucleus of each cell. Each chromosome has hundreds to thousands of genes. Each gene carries DNA (instructions for making proteins). Humans have an estimated 30,000 genes, some of which are responsible for how the body uses medications. Even a small difference in a gene can have a large impact on the way the body responds to medication. Humans share around 99.5% of their genomes. The 0.5% difference accounts for millions of differences between the DNA of two individuals. The study of how your genes affect individual responses to medications is known as pharmacogenetics. 

What is pharmacogenetic testing? 

With pharmacogenetic testing, an individual’s blood or saliva is used by a laboratory to look for changes in genes. Pharmacogenetic testing can determine whether a medication is an effective treatment, the dose of medication you may need, if you are likely to have side effects from a medication, or the likelihood of drug-to-drug interactions.  

How do we know how genes affect medication response?  

Researchers compare the genomes of people taking the same medication. They look for sets of people with certain genetic variations who share common treatment responses. These responses are things like greater side effects, a need for a higher dose, no benefit from the drug, or the optimal duration of treatment.  

How is pharmacogentic testing being used?

Doctors in primary care, mental health, cardiology, asthma, and cancer use pharmacogentic information to help prescribe the best drug for the patient. This information is used along with clinical factors, such as the patient’s age, weight, sex, and diagnosis. This helps avoid the trial-and-error approach and decreases injuries or deaths due to drug reactions.  

Will having genetic testing affect my ability to get health insurance in the future? 

A federal law, the Genetic Information Nondiscrimination Act (GINA), makes it illegal for insurance companies to discriminate based on genetic information. Life insurers and the military may still use this information. 

How often should genetic testing be done?  

Once. Genetic testing is based on DNA, which is inherited from an individual’s parents and does not change. 

What are the challenges of pharmacogenetic testing? 

Pharmacogentic testing is still in its infancy. Identification of a genetic change does not necessarily indicate an absolute diagnosis of non-response or side effects. Current tests only show known variants in genes. Genes are not the only factor that influences the body’s response to medication. Age, lifestyle, health, and environmental factors can also affect medication.  

Only 11% of doctors have discussed personalized treatment options through pharmacogentic testing. This may be because of the limited office time doctors have with patients. It may also be due to the lack of knowledge and experience practitioners have with pharmacogenetic testing. Cost of testing and insurance coverage are other possible factors. 

 References 

Clifton, J. M., VanBeuge, S. S., Mladenka, C. and Wosnik, K. K. (2010), The Genetic Information Nondiscrimination Act 2008: What clinicians should understand. Journal of the American Academy of Nurse Practitioners, 22: 246–249.  

Mills, R., Voora, D., Peyser, B., & Haga, S. B. (2013). Delivering pharmacogenetic testing in a primary care setting. Pharmacogenomics and Personalized Medicine, 6, 105–112.  

   
National Institute of General Medical Sciences: Frequently Asked Questions about Pharmacogenomics (http://www.nigms.nih.gov/research/FeaturedPrograms/PGRN/Background/pgrn_faq.htm)   
National Institutes of Health Genetics Home Reference: What is Pharmacogenomics? (http://ghr.nlm.nih.gov/handbook/genomicresearch/pharmacogenomics)   
PharmGKB: Clinical Pharmacogenetics Implementation Consortium (CPIC) Guidelines (http://www.pharmgkb.org/page/cpic)   
Mayo Clinic: Personalized Medicine and Pharmacogenomics (http://www.mayoclinic.com/health/personalized-medicine/CA00078)   
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Written by Dr. Kelly Wosnik, NP-C

Dr. Wosnik is the owner of Bristol Health, a mental health clinic in Orem, Utah. She received her bachelor’s and master’s degrees in nursing from Brigham Young University and her Doctor of Nursing Practice (DNP) from the University of Utah. In addition to her medical practice, she is the founder of CCD Smiles, a nonprofit organization that helps individuals with cleidocranial dysplasia.

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