HOW GENETIC MEDICINE CAN HELP OUR HEALTH
Genetic medicine involves testing and examining your DNA, the chemical database that carries instructions for your body's functions. Genetic testing can reveal changes or alterations in your genes that may cause illness or disease. Thanks to the great scientific breakthrough of 2003, when the human genome was decoded, laboratory tests that use rapid gene sequencing technologies have emerged providing the healthcare community with more than 900 genetic tests available to check for genes that predict ‘risk’ for certain diseases and conditions.
For those interested in knowing their chemical database, their DNA, there are companies such as DNA Traits, Gene Planet, DNA DTC and 23andme, that offer do-it-yourself tests to screen for future health risks. Some companies also provide information about your ancestry, highlight a wide range of personal traits and characteristics, and predict how you’ll respond to certain medications? Are you interested?
WHY WOULD YOU BE INTERESTED IN YOUR GENETIC MATERIAL: DNA?
Are you not worried about what you may find out? Could you be in danger of having the same condition that cost the life of your loved family member such as Cancer, Heart Disease, Alzheimer ’s disease? Do you really want to know? Genetic tests may show that you're at increased risk for a condition for which there's no prevention strategy or cure, and as the National Human Research Genome Institute notes, “Such knowledge may help you plan your life, but it may also make you and your loved ones anxious or depressed causing more harm than good.”
Millions of people will have done genetic testing by the end of this year. But does it make sense for people to screen themselves for future health threats without a healthcare provider’s guidance? How do you think you would handle the answers you receive?
Supporters of DNA testing say that this type of screening provides actionable insights that people can use to protect themselves from future risks, initiate prevention rather than waiting until a disease strikes. Critics question the scientific validity of the results as they are not put in the context of the tests' accuracy.
The Federal Trade Commission, which regulates makers of genetic tests, cautions that some home tests lack and others provide results lifestyle and environment. It is well known that some genes may not express themselves unless they are activated by an environmental effect. As a result, some results of genetic tests can provide a ‘misleading’ picture of future health threats, either by falsely reassuring people with undiscovered risk factors that there's nothing to worry about or needlessly alarming those with undiscovered protective factors. It is also important to understand that many parts of the genetic puzzle remain unsolved. Talking to your doctor or a genetic counselor about what you will do with the results is an important step in the process of genetic testing.
If you are interested in testing your genes, or are being tested for a genetic disorder that runs in families, you may want to consider discussing your decision to undergo genetic testing with your family. Gather as much information about your health as possible. Having these conversations before testing can give you a sense of how your family might respond to your test results and how it will affect them. But, most importantly be prepared for the result and how it will affect you.
TRADITIONAL GENETIC TESTING
There are some medical conditions that run in families. Some are well described to be due to a change in genes or what is called a mutation. There are a number of different types of genetic tests available today. They can be done for different reasons:
1. Diagnostic testing: Can identify a genetic condition or disease that is making the person ill at the time or in the future will make the person ill. It can help treat the disorder or at least manage it. If you have symptoms of a disease that may be caused by genetic alterations, genetic testing can reveal if you have the suspected disorder. Examples of disorders for which genetic testing may be used to confirm a diagnosis include adult polycystic kidney disease, iron overload (hemochromatosis) and Charcot-Marie-Tooth disease.
2. Predictive and Symptomatic testing: Can test for genetic differences that increase a person’s chance of developing specific diseases. This type of genetic testing may help provide information about a person’s risk of developing a disease, and can help in decisions about lifestyle and health care. Yet the results are not conclusive about the condition or disease. This kind of testing is considered when you have a family history of a genetic condition, and you want to undergo genetic testing before you have symptoms. This test may show if you're at ‘risk’ of developing that condition.
3. Carrier testing: This type of testing can tell a person if they “carry” a genetic change that can cause a disease. Carriers usually show no signs of the disorder; however, they can pass on the genetic variation to their children, who may develop the disorder or become carriers themselves. If you have a family history of a genetic disorder — such as sickle cell anemia or cystic fibrosis — or you are in an ethnic group that has a high risk of a particular genetic disorder, you may choose to have genetic testing before you have children. An expanded carrier screening test can detect genes associated with a wide variety of genetic diseases and mutations.
4. Pre-natal testing: This testing is offered to pregnant mothers to help identify if the unborn child has a possible genetic disease. These tests are available and can detect some types of abnormalities in your baby's genes. Down syndrome and trisomy 18 are two genetic disorders that are often screened for as part of prenatal genetic testing.
5. Pre-Implantation testing: Also called pre-implantation genetic diagnosis, this test may be used when you attempt to conceive a child through in vitro fertilization This kind of testing is done for women to determine if embryos for implantation carry genes that could cause disease. In-vitro fertilization means that eggs are removed from a woman and sperm are collected from a man. The eggs are then fertilized with the sperm outside the body to create embryos. The embryos are then screened for genetic abnormalities. Embryos without abnormalities are implanted in the uterus in hopes of achieving pregnancy.
6. Newborn screening: This is the most common type of genetic testing. In the United States, all states require that newborns be tested for certain gene abnormalities that cause specific conditions. This screening tool is used to test babies one or two days after they are born to find out if they have certain diseases known to cause problems with health and development. This type of genetic testing is important because if results show there's a disorder such as congenital hypothyroidism or phenylketonuria (PKU), care and treatment can begin right away.
7. Pharmacogenetic testing: This testing is very cutting edge. It is used to test the genes that give information about how certain medicines are processed in a person’s body. This is individualized medicine at its best. When this testing is done, the healthcare provider can have insight into how your specific body metabolizes medicines and therefore be more accurate when deciding on what the best and most unique and most importantly the one that work best with a person’s genetic makeup. For example, genetic testing is now available to guide treatments for certain cancers, and determine how your liver metabolizes drugs. This type of genetic testing may help determine what medication and dosage will be most effective and beneficial for each unique patient.
8. Research genetic testing: As the word implies, this kind of testing helps scientists learn more about how genes contribute to health and disease, as well as develop gene-based treatments. Sometimes the results do not directly help the research participant, but they may benefit others in the future by helping researchers expand their understanding of the human body.
HOW AER GENETIC TESTS DONE?
Your doctor, medical geneticist or nurse practitioner may administer a genetic test. You can also buy commercial kits offered directly to consumers. Depending on the type of test, a sample of your blood, or urine, skin, cheek swab, amniotic fluid or other tissue, such as hair, can be collected and sent to a lab for analysis.
1. Blood sample: A member of your health care team obtains the sample by inserting a needle into a vein in your arm, and blood is drawn into a test tube and sent for analysis. In newborns, the genetic screening tests are done using a blood sample taken by pricking the baby's heel.
2. Cheek swab: In some situations, a swab sample from the inside of your cheek is collected for genetic testing. This swab uses the cells in your mucous membranes and the DNA from those cells suffice to provide useful information.
3. Amniocentesis: This prenatal genetic test is done on pregnant mothers and measures the genes in the fluid in which the unborn baby is swimming. This fluid is called the amniotic fluid. The procedure is called amniocentesis. It is done by a specialized doctor who inserts a thin, hollow needle through the abdominal wall and into the uterus. A small amount of amniotic fluid is then withdrawn into a syringe, and the needle is removed. The fluid is then sent for testing.
4. Chorionic villus sampling. For this prenatal genetic test, your doctor takes a tissue sample from the placenta. Depending on your situation, the sample may be taken with a tube (catheter) through your cervix or through your abdominal wall and uterus using a thin needle.
The amount of time it takes for you to receive your genetic testing results will depend on the type of test and your health care facility. Talk to your doctor before the test about when you can expect the results. The lab will likely provide the test results to your doctor in writing. Your doctor can then discuss them with you.
NON-TRADITIONAL GENETIC TESTING
Some types of genetic testing can be purchased directly by the health care consumer, and unfortunately, more often than not, the results are not interpreted with the health care provider. This is because the communication between the patients as a consumer is ‘not comfortable’ speaking with their doctor what they are doing, which is unfortunate. More often than not, a person has to make sense of the results without the advice of their doctor.
The cost can sometimes be prohibitive, and although some genetic testing is covered by insurance, not all insurance companies cover all types of genetic testing. So, before you have a genetic test, check with your insurance provider to see what will be covered. This will avoid unpleasant surprises.
In the United States, the federal Genetic Information Non-discrimination Act (GINA), (http://www.genome.gov/24519851) helps prevent health insurers or employers from discriminating against the person being tested and getting their results. Most states offer additional protection for health care consumers that undergo genetic testing. More recently there have been some FDA regulations that have started to control these tests.
HOW TO UNDERSTAND THE RESULTS OF GENETIC TESTING
The results provided to you after genetic testing can have several types of results:
1. Positive results
2, Negative results
3. Inconclusive results
When the result of the genetic test is POSITIVE, this means the test was able to detect the genetic alteration that was suspected, and the reason for the test. The steps that need to be taken after you receive a positive result will depend on the reason you underwent genetic testing. If the purpose was to diagnose a specific disease or condition, a positive result will help you and your doctor determine the right treatment and management plan.
If you were tested to find out if you are carrying an altered gene that ‘could’ potentially cause disease in your child or yourself for that matter, and the test is positive, it is best you consult with a specialist in the field of genetics and in the field of the specific disease that is being tested for. These specialists can then help you determine your child's or your own risk of actually developing the disease. The test results can also provide information to consider as you and your partner make family planning decisions.
If the genetic test is done to determine if you ‘might’ develop a certain disease, a positive test doesn't necessarily mean you will get that disorder. This is really IMPORTANT FOR YOU TO CONSIDER….. For example, having a breast cancer gene (BRCA1 or BRCA2) means you are at high risk of developing breast cancer at some point in your life, but it doesn't indicate with CERTAINTY that you will get breast cancer. However, there are some conditions, such as Huntington's disease, for which having the altered gene DOES indicate that the disease will eventually develop. This is why it is very important to have a good doctor patient relationship where you can feel comfortable speaking with your doctor about these tests and what the next step should be to protect your health and your future children.
Talk to your doctor about what a positive result means for you. In some cases, you can make lifestyle changes that may decrease your risk of developing a disease, even if you have an altered gene that makes you more susceptible to a disorder. Results may also help you make choices related to family planning, careers and insurance coverage. In addition, you may choose to participate in research or registries related to your genetic disorder or condition. These options may help you stay updated with new developments in prevention or treatment.
A negative result means a genetic alteration was NOT detected by the test. But a negative result doesn't ‘guarantee’ that you don't have an alteration. The accuracy of genetic tests to detect alterations varies, depending on the condition being tested for and whether or not an alteration has been previously identified in a family member. Even if you don't have the genetic alteration, that doesn't necessarily mean you will never get the disease. For example, people who don't have a breast cancer gene (BRCA1 or BRCA2) can still develop breast cancer. Also, genetic testing may not be able to detect all genetic defects.
In some cases, a genetic test may not be able to provide helpful information about the gene in question. Everyone has variations in the way genes appear, this is called polymorphism. More often than not, these variations don't affect your health. But sometimes it can be difficult to distinguish between a disease-causing gene alteration and a harmless gene variation. In these situations, follow-up testing may be necessary. No matter what the results of your genetic testing, I encourage you talk with your doctor or genetic counselor about questions or concerns you may have. This will help you understand what the results and what they mean for you and your family.
RESOURCES ABOUT GENETIC TESTING AVAILABLE TODAY INCLUDE:
GeneTests - www.genetests.org
National Human Genome Research Institute – www.genome.gov/health
National Cancer Institute – www.cancer.gov/cancertopics/UnderstandingCancer/genetesting
Genetics Home Reference – www.ghr.nlm.nih.gov/handbook/testing
Medline Plus/Genetic Testing – www.nlm.nih.gov/medlineplus/genetictesting.html
Genetic and Rare Diseases Information Center (GARD) : www.rarediseases.info.nih.gov/GARD
Thank you for reading.
In my next blog, I will discuss genetic testing and nutrition, genetic testing and obesity and how you can use genetic testing to determine the best diet JUST FOR YOU.
Dr. Margarita Ochoa-Maya, MD