Overview of Genetic Testing

Argyro Bogiantzis, Pharm.D. Candidate; Whitney Oakley, Pharm.D. Candidate

What is genetic testing?

Genetic testing is a voluntary medical exam that can identify changes in chromosomes, genes, or proteins. There are several methods used for genetic testing including those of molecular, chromosomal, and biochemical nature. A molecular genetic test will study single genes, or short lengths of DNA, to identify variations or mutations that lead to a genetic disorder. On the other hand, a chromosomal genetic test examines whole chromosomes, or long lengths of DNA, to observe any large changes, such as an extra copy of a chromosome. A biochemical genetic test identifies the amount or activity level of proteins, which can display changes to the DNA if the amount, or activity level, is abnormal.1 By examination of changes in chromosomes, genes, and proteins using the methods listed above, health care professionals can identify an increased risk for health issues, choose specific treatments, or assess responses to treatments for any given individual. There are many different types of genetic tests. The types of genetic tests include the following:

  • Diagnostic testing: identifies the disease a person may currently have. The results from this test will help the health care professional make choices on how to treat or manage the individual’s treatment.
  • Predictive and pre-symptomatic testing: identifies gene changes that increase a person’s risk of developing diseases. The results from this test will provide information about a person’s risk of developing a specific a disease, which can help in making decisions about lifestyle and healthcare.
  • Carrier testing: identifies people who “carry” a change in a gene that is linked to a disease. Carriers may show no symptoms of the disease, but they can pass the gene change onto their children. The children can then either develop the disease, or become carriers themselves.
  • Prenatal testing: identifies if a fetus may have a certain disease, and is offered during pregnancy.
  • Newborn screening: identifies genetic disorders that can be treated in the beginning of life.
  • Pharmacogenomic testing: identifies how certain medicines are processed by a person’s body. The results from this test can help the healthcare professional choose medications that will work best with that individual’s genetic makeup.2
  • Genetic ancestry testing: identifies DNA variations that can provide clues to where a person’s ancestors might have come from. Ancestral testing is completed through either Y chromosome testing, mitochondrial DNA testing, or single nucleotide polymorphism testing.1

There are many other types of genetic tests, but those listed above are the ones most commonly done.

Which patients can benefit from genetic testing?

The patients that can benefit from genetic testing are those with a known family history of a genetic disease, since those individuals are at a higher risk of developing the genetic disease. Couples that wish to start a family will also benefit from genetic testing to see if either parent is a carrier for a specific genetic disorder, and can therefore assess what amount of risk their child has of developing a genetic disorder.2

What does genetic testing have to do with my medications?

Genetic testing may give some insight as to why certain medications work better or worse for a patient. Medications may work differently for people due to any genetic changes caused by the amount or activity level of certain proteins, called enzymes, which are responsible for the activation, as well as elimination, of drugs in the body.2

Do I really need these tests?

The decision on whether or not to undergo these tests can be quite complicated. One way to choose may be by receiving a referral from your doctor when they suspect that a disease may run in your family. This would mean that a trusted healthcare professional is letting you know that they think you would benefit from such tests. A genetic counselor or geneticist may be a good first resource to ask questions of regarding the process of genetic testing. In addition to providing you with information on whether or not you are a good candidate for genetic testing, they can help you understand the basics behind how these tests work, help you manage your emotions during each step of the process, explain what your results ultimately mean for you, and also guide you in your next steps after receiving the results.

Another way to help make this decision involves weighing out the pros and cons. Benefits to genetic testing include finding definitive proof that you either will or will not develop a disease, allowing for proper screening and treatments to begin at an earlier point in time, and helping you decide whether or not to have a child based on the genetic possibilities that the baby could acquire. Some cons associated with the process and results of genetic testing deal with feelings of helplessness, costs that can become a burden, possible discrimination by insurance companies, and the fact that it can not determine how severe your form of the disease will be.2

How do I get these tests?

After you have been properly informed about all aspects of genetic testing, and have decided to proceed, a healthcare professional, such as a physician, nurse practitioner, or geneticist, will order the tests for you. The testing facility will require some form of DNA from you. This could be a small amount of blood, skin, or hair. The next step is to wait for your doctor to provide you with the written results from the laboratory.3

Will my insurance cover this?

Most of the time, a given insurance company will cover the costs of genetic testing as long as a doctor has initiated a request for one. However, each individual company has its own list of which types of testing they will cover. It is in your best interest to find out which tests are covered, along with any kind of changes you can expect to occur to your policy coverage based on your results, prior to submitting any claims for genetic testing. If you are not satisfied with the changes, if any, that would be applied by your insurance provider after obtaining results, then you should consider an out-of-pocket payment instead.4

Sources of Information

1. Genetics Home Reference [Internet]. Bethesda. U.S. National Library of Medicine. National Institutes of Health. What is genetic testing?; [2018 Feb 13; cited 2018 Jan 20]; [about 1 screen]. Available from: https://ghr.nlm.nih.gov/primer/testing/genetictesting

2. FAQ About Genetic Testing [Internet]. National Human Genome Research Institute (NHGRI). National Institute of Health; [2017 July 5; cited 2018 Jan 20]; [about 2 screens]. Available from: https://www.genome.gov/19516567/faq-about-genetic-testing/

3. Genetics Home Reference [Internet]. Bethesda. U.S. National Library of Medicine. National Institutes of Health. How is genetic testing done?; [2018 Feb 13; cited 2018 Feb 17]; [about 1 screen]. Available from: https://ghr.nlm.nih.gov/primer/testing/procedure

4. Genetics Home Reference [Internet]. Bethesda. U.S. National Library of Medicine. National Institutes of Health. Will health insurance cover the costs of genetic testing?; [2018 Feb 13; cited 2018 Feb 17]; [about 1 screen]. Available from: https://ghr.nlm.nih.gov/primer/testing/insurancecoverage