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What is an Alpha Fetoprotein (AFP) Test? |
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Written by Gary Presant, MD
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Sunday, 04 October 2009 |
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An alpha fetoprotein, or AFP, test measures the level of the AFP protein. AFP protein is found in everyone's blood. Higher levels are found in the blood of pregnant women, fetuses, and young children. AFP levels can also be elevated in the blood of people with certain diseases and conditions.
AFP can also be measured in the amniotic fluid of a pregnant woman.
Amniotic fluid is the substance that surrounds a baby in the womb.
Who is a candidate for the test?
An AFP test is routinely ordered for pregnant women around the 16th week of pregnancy. It is used to screen for the following conditions in the fetus:
- abnormalities in the urinary tract
- defects in the abdominal wall, esophagus, or bowel
- Down syndrome and other chromosomal abnormalities
- neural tube defects, such as spina bifida
The AFP test can also be used to screen for certain cancers. And it can be used to help monitor certain cancers that are being treated.
How is the test performed?
A blood sample needs to be taken in order to measure the AFP. The blood is usually drawn from a vein in the forearm or the hand. First, the skin over the vein is cleaned with an antiseptic. Next, a strong rubber tube, or tourniquet, is wrapped around the upper arm. This enlarges the veins in the lower arm by restricting blood flow through them. A very thin needle is gently inserted into a vein, and the tourniquet is removed. Blood flows from the vein through the needle and is collected into a syringe or vial. The blood sample is sent to the laboratory for testing. After the needle is withdrawn, the puncture site is covered for a short time to prevent bleeding.
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