As the fields of genetics and personalized medicine progress, the number of genetic tests available for certain conditions continues to grow. Currently, there are approximately 1300 genetic tests in use, and the identification of disease-causing genes is still advancing rapidly. In fact, it is almost guaranteed that most people, either as a newborn or an adult, will be offered a genetic test sometime in their life.
While the prospect of using genetics to predict and better diagnose disease is certainly exciting, taking a genetic test is not a decision that should be taken lightly. It requires careful consideration and often the knowledge of a medical professional trained in genetic counseling to help you prepare for and understand the results. It is also important to understand what kinds of test are available, and what they can and cannot tell you.
To understand what kind of information a genetic test can provide, it is important to look at how the study of genetics and their contribution to disease has developed. While using genetics to diagnose disease is a hot topic right now, some forms of genetic testing have been available for over fifty years. By the late 1950s, techniques for the study of human chromosomes had been developed, making it possible to diagnosis conditions like Down syndrome. This technique, called chromosome analysis, allowed researchers to determine which chromosomal abnormalities were associated with certain conditions. Then, a health care provider could diagnose individuals by counting and observing their chromosomes and determining if there was an extra chromosome or a structural irregularity. These tests were and still are used primarily in pediatric clinics to help make a diagnosis in children already showing symptoms.
As scientists and health care providers grew more knowledgeable and laboratory techniques grew more sophisticated, it became possible to look at specific genes and associate them with certain disorders. Genes are responsible for coding the proteins and enzymes important for our growth and development. If there is a problem with a gene, the protein or enzyme it codes for may not be able to do the job that it was intended to perform and, therefore, problems can arise. Over time researchers have discovered what genes are responsible for or contribute to different genetic conditions, and developed tests to pinpoint these genes in individuals.
Now that this technology is available, it is common to wonder if it would be appropriate to have a genetic test, and if so, which one? There are actually many points during a person’s lifetime when a genetic test may be offered. Couples routinely face several testing options during their pregnancy, either to diagnose a problem or indicate if there is a higher risk of a problem. At birth, the majority of babies have a newborn screening, which primarily looks for several genetic disorders called metabolic conditions. For instance, babies are screened for a condition called phenylketonuria (PKU). In PKU, the gene that is responsible for producing an enzyme that breaks down phenylalanine does not work properly. Therefore, phenylalanine builds up in the person’s brain and, if left untreated, can cause mental retardation. Babies diagnosed at birth with PKU are immediately put on a low phenylaline diet, which prevents the build up of phenyalanine in the brain and subsequent problems.
In addition to newborn screening, some babies may have additional genetic testing if they are suspected to have a genetic disorder based on the presence of a birth defect or specific physical features. As a child grows and develops, genetic testing may be appropriate if their speech is delayed or if they are having difficulty walking and developing their motor skills. For instance, a common cause of mental retardation and autism in males is a condition called fragile X syndrome. A test can be performed to determine if the gene that causes this condition is working correctly. While fragile X can’t currently be cured, a diagnosis provides parents with an explanation for their child’s problems and more knowledge of what to expect in the future.
People may also choose to have a genetic test if there is a disorder or illness in their family history that could be hereditary, such as breast or colon cancer. For instance, in the case of breast and ovarian cancer, a person might consider genetic testing if they have multiple family members with breast or ovarian cancer, and if they were diagnosed at a young age. For some people, finding out they carry a gene that increases their risk for cancer can be very empowering. It can allow them to make decisions about their health care and take preventive measures, such as increased surveillance or surgery, if available.
However, there are many different factors that must be taken into account when assessing a person’s risk for cancer. If someone is concerned about an illness or disorder in his or her family, the first step is to meet with a genetic counselor who can take a detailed family history and determine if a person is actually at an increased risk. Genetic counselors are masters-level health care professionals who have advanced training in medical genetics and genetic counseling. If a person is determined to be at a higher risk, genetic testing is offered and a genetic counselor can then help to weigh the pros and cons of proceeding with the test.
In fact, The National Society of Genetic Counselors (NSGC) recommends that all individuals who are considering genetic testing meet with someone who is specifically trained in genetics to help them understand and interpret their results. In addition to providing risk assessment and counseling to individuals and families, they explain the benefits and limitations of genetic testing and communicate complex disease information in easily understood terms. Genetic counselors also serve as patient advocates and refer individuals and families to community or state support services.
Above all, choosing to have a genetic test should be a thoughtful and informed decision. Meeting with a genetic counselor or a health care provider who has expertise in genetics before proceeding with testing will allow one to explore his or her personal benefits and risks. While genetic testing may be the right choice for many, it is not always the right choice for everyone. In the case of a genetic condition where there is treatment or one can make more informed medical management decisions, genetic testing can be very valuable. In other cases, where there is no treatment, it may not be seen as a benefit. However, many people feel empowered by knowing their risk for developing a disorder, even in the cases where there is no treatment.
With the continued advancement in the field of genetics and personalized medicine, the opportunities to test for and treat genetic disorders will increase. Knowing who to go to and what questions to ask are the first steps in navigating the genomic landscape.
In addition to meeting with a genetic counseling, NSGC recommends that all individuals considering a genetic test should ask five key questions before they proceed:
1. Is the correct test being ordered? Discuss with your genetic counselor which test(s) specifically address your medical concerns. There are many genetic tests, each testing for a different medical condition. If the wrong test is ordered it may not give you any information about your medical concerns.
2. How valid are the test results? Some test results will be clear, while others will be inconclusive or require additional testing.
3. What decisions might you need or want to make once you know the results? Consider the implications of having the test and the impact it could have on you and your family—medically, emotionally, and in terms of life planning.
4. What are the credentials of the person who will give you the test results? It is important that someone who has expertise in genetics helps you understand and interpret your test results.
5. Once you have the test results, what are your next steps? Take time to learn more about what these results mean for your health and who else in your family may be at risk and need this information.
To find a genetic counselor in your area visit www.nsgc.org.