A genetic test examines the
DNA (deoxyribonucleic acid) of a person's cells.
Genetic testing can identify changes in
genes or can 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
for certain diseases. Certain changes in genes or chromosomes may
cause medical problems.
Why It Is Done
A genetic test is done to:
- Find out if people who have a
family history of a specific disease are likely to pass that disease on to
their children (carrier identification). Information
obtained from this type of testing can help guide a couple as they make
decisions regarding pregnancy.
- Find out if a
fetus has a disorder such as
Down syndrome (prenatal testing). Information obtained from this type of testing can help guide
a couple as they make decisions regarding pregnancy.
- Check for
various metabolic diseases, such as
phenylketonuria (PKU) (newborn screening). Information obtained from newborn screening can help guide
medical treatment to ensure the best possible outcome for the
- Check to see if you carry a genetic change that increases your
risk for a disease, such as breast cancer or
Huntington's disease, later in life (late-onset disease testing). This might be important to you if
you have a parent or other relative diagnosed with the disease. Information
obtained from this type of testing can help you make decisions about disease
prevention or future childbearing.
- Help diagnose hypertrophic cardiomyopathy (HCM) or screen for HCM in close relatives of a person who has the disease.
- Check for genetic changes that may affect your treatment for
diseases such as
HIV or some cancers.
- Check for a genetic change that may affect how a medicine, such as clopidogrel, will work.
How To Prepare
You do not need to do anything before you have this test.
Talk with 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
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 who has 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.