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Fetal alpha globulin; AFP
Alpha fetoprotein (AFP) is a protein normally produced by the liver and yolk sac of a fetus. AFP levels decrease soon after birth. AFP probably has no normal function in adults.
A test can be done to measure the amount of AFP in your blood.
See also: Quadruple screen
Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.
Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.
Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.
There is no special preparation.
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Your doctor may order this test to:
During pregnancy, this AFP test can be done along with the examination of amniotic fluid (amniocentesis) to help detect fetal spina bifida or other birth defects.
The normal values in males or nonpregnant females is generally less than 40 micrograms/liter.
Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
Greater-than-normal levels of AFP may be due to:
During pregnancy, abnormal levels of AFP (as part of a quadruple screen) may be due to:
Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
Simpson JL, Otaño L. Prenatal genetic diagnosis. In: Gabbe SG, Niebyl JR, Simpson JL, eds. Obstetrics - Normal and Problem Pregnancies. 5th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2007:chap 7.
Lee P, Pincus MR, McPherson RA. Diagnosis and management of cancer using serologic tumor markers. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 21st ed. Philadelphia, Pa: Saunders Elsevier; 2006:chap 74.
Cunnigham FG, Leveno KL, Bloom SL, et al . Prenatal diagnosis and fetal therapy. In: Cunnigham FG, Leveno KL, Bloom SL, et al, eds. Williams Obstetrics. 22nd ed. New York, NY; McGraw-Hill; 2005:chap 13.
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