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.
How It Is Done
A genetic test can be done using almost
any cell or tissue from the body.
Blood sample from a heel stick
If genetic testing
is done on a baby, a heel stick usually is 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.
Blood sample from a vein
The health professional
drawing your blood will:
- Wrap an elastic band around your upper arm to
stop the flow of blood. This makes the veins below the band larger so it is
easier to put a needle into the vein.
- Clean the needle site with
- Put the needle into the vein. More than one needle stick
may be needed.
- Attach a tube to the needle to fill it with
- Remove the band from your arm when enough blood is
- Apply a gauze pad or cotton ball over the needle site as
the needle is removed.
- Apply pressure to the site and then a
Cell sample from a fetus
For this type of testing,
cells are collected from the fetus using
chorionic villus sampling.
To learn more, see: