Genetic Test: How It Is Done

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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 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.

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 alcohol.
• Put the needle into the vein. More than one needle stick may be needed.
• Attach a tube to the needle to fill it with blood.
• Remove the band from your arm when enough blood is collected.
• Apply a gauze pad or cotton ball over the needle site as the needle is removed.
• Apply pressure to the site and then a bandage.

Cell sample from a fetus

For this type of testing, cells are collected from the fetus using amniocentesis or chorionic villus sampling. For more information about amniocentesis, see the medical test Amniocentesis or Chorionic Villus Sampling.

Last updated:	April 26, 2007
Author:	Maria G. Essig, MS, ELS
Reviewed By:	Joy Melnikow, MD, MPH - Family Medicine, Renee H. Martin, PhD - Medical Genetics
Editors:	Susan Van Houten, RN, BSN, MBA, Tracy Landauer