Why do genetic testing?
A genetic test is generally performed so a person can find out if they suffer from a specific disease or condition.
DNA serves as the body's instruction manual. Nearly every cell in a person's body has the same DNA. Genes are segments of DNA found in chromosomes, and they control growth and help you stay healthy.
A genetic test is sometimes run to help find a gene that's damaged or missing something. The test can help determine whether you are suffering from a chromosomal defect, including whether you're missing or have an extra chromosome, or maybe if small bits of chromosomes are missing.
Parents of a child with an intellectual disability or a facial characteristic that isn't typical to child development might bring their child in for a genetic test. Sometimes, pregnant mothers have genetic testing run to determine whether their child might develop a birth defect or rare disorder.
Also, families with high rates of cancer in their history might undergo genetic tests to determine what risk there is of passing genes onto the next generation.
To begin, you'll meet with a team of medical professionals trained in genetics testing. You'll be asked questions about your family history, so it's important to come prepared.
Generally, a medical professional will take a blood sample. If the genetic test is for a pregnant mother, a doctor might collect fluid from the mother's abdomen. This process is known as amniocentesis, where a needle is used to collect fluid near the uterus. This is done with guidance from an ultrasound that shows where the baby is inside the mother's womb.
There are several types of tests that a genetics testing lab can run. Generally, the most popular types of tests are chromosome tests, in which whole chromosomes or very long lengths of DNA are tested; gene tests, in which individual genes or relatively short lengths of DNA or RNA are tested; or biochemical tests, in which protein levels or enzyme activities are tested.
Does it hurt?
If you're simply having blood drawn, it will depend on your pain tolerance. If you're undergoing amniocentesis, you might experience some discomfort. When the needle is inserted, you might feel a stinging sensation. You might also feel cramping when the needle enters your uterus.
What are the risk factors?
There is a small risk of miscarriage associated with amniocentesis. The test is generally offered to women between the 15th and 20th weeks of pregnancy who are at increased risk for chromosome abnormalities, such as women who are older than 35 years at delivery, or women who have had an abnormal maternal serum screening test, indicating an increased risk for a chromosomal abnormality.
Also with this procedure, there's a risk of needle injury, but serious needle injuries are rare. In rare cases, amniotic fluid leaks through the vagina after the procedure.
What's the follow-up?
Your test results are generally ready anywhere from a few hours to two weeks, depending on the urgency of the information. For example, if doctors need more information on a newborn baby whose health is unstable, those results might be ready within hours.
After you get your results, you might meet with a genetics counselor, a person who can help you and your family understand the diagnosis. In many cases, the results of a genetics test affect more than just the person being tested, for results can point to a genetic disease other family members might have.
Most of the follow-up care you or your child receive will depend largely on the results and what you and your doctor decide is best. It's important to ask any questions you have and be up front with your doctor.
Sources: Dr. Sanjay Bidichandani, chief of genetics at University of Oklahoma Health Sciences Center pediatrics department; U.S. National Library of Medicine; National Human Genome Research Institute; and the American Academy of Family Physicians; Lucille Packard Children's Hospital at Stanford; the Mayo Clinic