A genetic test examines the DNA (deoxyribonucleic acid) of a person's cells. Genetic testing can identify abnormal genes, or analyze the number, arrangement, and characteristics of the chromosomes. Testing may be performed on samples of blood, semen, urine, saliva, stool, body tissues, bone, or hair.
You inherit half of your genetic information from your mother and the other half from your father. Genes, alone or in combination, determine what features (genetic traits) a person inherits from his or her parents, such as blood type, hair color, eye color, and other characteristics, including risks of developing certain diseases. Certain changes in genes or chromosomes may cause medical problems.
A genetic test is done to:
No special preparation is needed before having this test.
Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).
Since the information obtained from a genetic test can have a profound impact on your life, you may want to see a doctor who specializes in genetics (geneticist) or a genetic counselor. This type of counselor is trained to help you understand your risk for developing a genetic disease or having a child with an inherited (genetic) disease, such as sickle cell disease, cystic fibrosis, or hemophilia. A genetic counselor can help you make well-informed decisions. Ask to have genetic counseling before making a decision about genetic testing.
A genetic test can be done using almost any cell or tissue from the body.
If genetic testing is done on a baby, a heel stick will be done instead of a blood draw from a vein. For a heel stick blood sample, several drops of blood are collected from the heel of the baby. The skin of the heel is cleaned with alcohol and then pricked with a small, sterile lancet. Several drops of blood are collected inside circles on a specially prepared piece of paper. When enough blood has been collected, a gauze pad or cotton ball is placed over the puncture site. Pressure is applied to the puncture site briefly, and then a small bandage is usually placed over it.
The health professional drawing your blood will:
For this type of testing, cells are collected from the fetus using amniocentesis or chorionic villus sampling. For more information about amniocentesis, see the topic Amniocentesis or Chorionic Villus Sampling.
The baby may feel a brief sting or a pinch when the lancet pricks the skin. While the blood is being collected, there is very little or no discomfort.
You may feel nothing at all from the needle puncture, or you may feel a brief sting or pinch as the needle goes through the skin. Some people feel a stinging pain while the needle is in the vein. But many people do not feel any pain, or have only minor discomfort, once the needle is positioned in the vein. The amount of pain you feel depends on the skill of the health professional drawing the blood, the condition of your veins, and your sensitivity to pain.
The collection of DNA from saliva, urine, or semen does not cause discomfort.
There is very little risk of complications from having blood drawn from a heel stick. A small bruise may develop at the puncture site.
There is very little risk of complications from having blood drawn from a vein.
There are no risks linked with collecting DNA from saliva, urine, or semen.
The information obtained from a genetic test can affect your life and the lives of your family in many ways, including:
The results of genetic testing depend on the type of test done. Genetic testing is used to:
Having a blood transfusion within a week before the test can interfere with your test or the accuracy of the results.
The information obtained from a genetic test can have a profound impact on your life. Genetic counselors are trained to help you understand your risk for having a child with an inherited (genetic) disease, such as sickle cell disease, cystic fibrosis, or hemophilia. A genetic counselor can help you make well-informed decisions. Ask to have genetic counseling before making a decision about genetic testing.
Other Works Consulted
- Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
- Skirton H, Patch C (2002). Genetics for Healthcare Professionals. Oxford, UK: BIOS Scientific Publishers Limited.
|Primary Medical Reviewer||Sarah Marshall, MD - Family Medicine|
|Specialist Medical Reviewer||Siobhan M. Dolan, MD, MPH - Reproductive Genetics|
|Last Revised||March 29, 2011|
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