FREE Newsletters

Print Friendly Version

Email a Friend

A-Z Health Guide from WebMD: Medical Tests





		Test Overview
		Health Tools
		Why It Is Done
		How To Prepare
		How It Is Done
		How It Feels
		Risks
		Results
		What Affects the Test
		What To Think About
		References
		Credits

Alpha-Fetoprotein (AFP) in Blood

Test Overview

An alpha-fetoprotein (AFP) blood test is done to determine the level of AFP in a pregnant woman's blood. AFP is a substance naturally produced by the liver of a fetus. The amount of AFP in the blood of a pregnant woman can help diagnose whether the fetus may have such problems as spina bifida, anencephaly, or Down syndrome. An AFP test can also be done to detect other, more rare conditions, such as chromosome (trisomy) syndromes or omphalocele, a congenital defect in which portions of a fetus's intestines protrude through the abdominal wall.

Normally, low levels of AFP can be found in the blood of a pregnant woman. No AFP (or only a very low level) is usually found in the blood of healthy men or healthy, nonpregnant women.

The level of AFP in the blood is often used in a maternal serum triple or quadruple screening test. Usually done between 16 and 18 weeks, these tests measure the amounts of three or four substances in a pregnant woman's blood. The triple screen measures alpha-fetoprotein (AFP), beta human chorionic gonadotropin (beta-HCG), and a type of estrogen (unconjugated estriol, or uE3). The quad screen measures these substances and the hormone inhibin-A. The levels of these substances—along with a woman's age and other factors—help estimate the risk that her child may have certain problems or birth defects.

In some cases a combination of screening tests is done in the first trimester to look for Down syndrome. The screening combines ultrasound measurement of the thickness of the fetus's neck (nuchal fold) and measurements of beta-HCG and a protein called pregnancy-associated plasma protein A. The accuracy of this screening is about the same as that of the second-trimester maternal serum quad screening.¹

Should I have the maternal serum screening test (triple or quad screen)?

Men and nonpregnant women

In men and nonpregnant women, alpha-fetoprotein in the blood can indicate the presence of certain types of cancer, especially cancer of the testicles, ovaries, stomach, pancreas, or liver. Increased levels of AFP may also be found in Hodgkin's disease, lymphoma, and renal cell cancer.

Health Tools

Health tools help you make wise health decisions or take action to improve your health.


	Decision Points focus on key medical care decisions that are important to many health problems.
	Should I have the maternal serum triple or quadruple test (triple or quad screen)?

Why It Is Done

The AFP test is done to:

Screen the fetus of a pregnant woman for brain or spinal problems (called neural tube defects). Such defects occur in about 2 out of every 1,000 pregnancies. The risk of a neural tube defect in a fetus is not related to the mother's age. Most women whose babies have neural tube defects have no family history of similar problems. When used to screen for birth defects, this test should be done between the 15th and 22nd weeks of pregnancy.
Screen the fetus of a pregnant woman for Down syndrome. A low AFP level can detect Down syndrome about 60% of the time. The chance of detecting Down syndrome increases to about 80% when results of the AFP test are considered along with the results from two other tests (estriol and human chorionic gonadotropin). When done together, these three tests are called the triple test.
Diagnose and monitor the effectiveness of treatment for some cancers, especially cancer of the testicles, ovaries, or liver. However, up to half of the people with liver cancer do not have high AFP levels.
Screen for liver cancer (called hepatoma) among people who have cirrhosis or chronic hepatitis B.

How To Prepare

No special preparation is required before having this blood test. If you are pregnant, you will be weighed before the blood test because the test results will be based on your weight. This test is also based on race.

How It Is Done

The health professional drawing 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.

How It Feels

You may feel nothing at all from the needle puncture, or you may feel a brief sting or pinch as the needle goes through the skin. Some people feel a stinging pain while the needle is in the vein. However, many people do not feel any pain (or have only minor discomfort) once the needle is positioned in the vein. The amount of pain you feel depends on the skill of the person drawing the blood, the condition of your veins, and your sensitivity to pain.

You may feel anxious while awaiting results of an alpha-fetoprotein test done to determine the health of your unborn baby.

Risks

Risks of a blood test

There is very little risk of complications from having blood drawn from a vein.

You may develop a small bruise at the puncture site. You can reduce the risk of bruising by keeping pressure on the site for several minutes after the needle is withdrawn.
Rarely, the vein may become inflamed after the blood sample is taken. This condition is called phlebitis and is usually treated with a warm compress applied several times daily.
Continued bleeding can be a problem for people with bleeding disorders. Aspirin, warfarin (Coumadin), heparin, and other blood-thinning medications can also make bleeding more likely. If you have bleeding or clotting problems, or if you take blood-thinning medication, tell your health professional before your blood is drawn.

Results

Normal

Normal alpha-fetoprotein (AFP) values may vary from lab to lab. Also, normal values vary according to the age of the fetus; a high or low AFP may mean that the age of the fetus has been miscalculated. An ultrasound may be done to determine fetal age more accurately. For more information, see the medical test Fetal Ultrasound.

**Alpha-fetoprotein in blood**
Men and nonpregnant women:	0–6.4 international units per milliliter (IU/mL)
	0–20 nanograms per milliliter (ng/mL)
	0–20 micrograms per liter (µg/L)
Women 15–22 weeks pregnant:	19–75 IU/mL
	7–124 ng/mL
	7–124 µg/L

In pregnant women, the amount of alpha-fetoprotein (AFP) gradually rises starting in the 14th week of pregnancy. It continues to rise until a month or two before giving birth, then it slowly declines. Values are generally slightly higher for black women than they are for white women. Values are slightly lower for Asian women than they are for white women. An accurate estimate of the age of the fetus is needed to interpret the alpha-fetoprotein value correctly.

The normal range of AFP values is adjusted for each woman's weight and race, whether she has diabetes (requiring injections of insulin), and the age of her fetus (gestational age). If the estimated age of the fetus is changed through ultrasound, the AFP must be adjusted. The middle of this adjusted range is called the multiple of median (MOM). An AFP value that is within 0.5 to 2.5 times the MOM value is considered normal for that woman. Each woman needs to look at the range of AFP values that is normal for her when she has an AFP test.

High values

High alpha-fetoprotein values in a pregnant woman can indicate:
- An inaccurate gestational age.
- A multiple pregnancy (such as twins, triplets).
- A fetus with a neural tube defect.
- That the fetus's intestines and other abdominal organs are being formed outside the body (called an abdominal wall defect). Surgery after birth will be needed to correct the defect.
- Fetal death.
In a nonpregnant adult, a high alpha-fetoprotein value can indicate cancer of the liver, testicles, or ovaries.
High values can also indicate liver disease, such as cirrhosis or hepatitis.
Alcoholism.

Low values

In a pregnant woman, a low level of alpha-fetoprotein can mean:

An inaccurate gestational age.
A fetus with Down syndrome.

What Affects the Test

Factors that can interfere with your test and the accuracy of the results include:

Smoking, which increases the level of alpha-fetoprotein in the blood.
A medical test in the past 2 weeks that used radioactive tracers.

What To Think About

The level of AFP in the blood is often used in maternal serum triple or quadruple screening test. Usually done between 16 and 18 weeks, these tests measure the amounts of three or four substances in a pregnant woman's blood. The triple screen measures alpha-fetoprotein (AFP), beta human chorionic gonadotropin (beta-HCG), and a type of estrogen (unconjugated estriol, or uE3). The quad screen measures these substances and the hormone inhibin-A. The levels of these substances—along with a woman's age and other factors—help estimate the risk that her child may have certain problems or birth defects. For more information about estriol and hCG, see the medical tests Estrogens and Human Chorionic Gonadotropin (hCG).
AFP is a screening test to look for possible problems in the fetus. Additional testing must always be done if the AFP results are abnormal. An ultrasound will be done to evaluate an abnormal AFP. If an ultrasound cannot detect the cause of the abnormal AFP, an amniocentesis may be done.
Normal AFP results do not rule out a neural tube defect or Down syndrome.
AFP test results are based on the age of the fetus. If a pregnant woman has a high AFP level, ultrasound may be used to estimate the age of the fetus as accurately as possible. An ultrasound often reveals a cause for the elevated AFP levels other than birth defects, such as a multiple pregnancy or underestimated fetal age. An ultrasound may also be done before the AFP test if the age of the fetus is not accurately known. For more information, see the medical test Fetal Ultrasound.
The amount of AFP in the amniotic fluid may also be measured using amniocentesis. Most women have normal AFP levels in the amniotic fluid, even though the levels may be abnormal in their blood. These women are at low risk of having a fetus with a neural tube defect. For more information, see the medical test Amniocentesis.
If abnormal levels of AFP are found in the blood of a pregnant woman, she should discuss the results and further plans with her health professional or genetic counselor. AFP test results can be abnormal, even when nothing is wrong with the fetus. Additional tests, such as amniocentesis, may be done if AFP blood levels are abnormal and ultrasound shows that there is one fetus and the estimated fetal age is correct.
In people with liver cancer or other types of cancer, a decrease in AFP may indicate a favorable response to treatment.

References

Citations

American College of Obstetricians and Gynecologists (2004). ACOG issues position on first-trimester screening methods. Available online: http://www.acog.org/from_home/publications/press_releases/nr06-30-04.cfm.

Credits

Author	Jan Nissl, RN, BS
Editor	Susan Van Houten, RN, BSN, MBA
Associate Editor	Daniel Greer
Associate Editor	Tracy Landauer
Primary Medical Reviewer	Renée M. Crichlow, MD - Family Medicine
Specialist Medical Reviewer	R. Hugh Gorwill, MD - Obstetrics and Gynecology
Last Updated	June 30, 2004

To	back to the top

Alpha-Fetoprotein (AFP) in Blood

Previous | Next

Last updated: June 30, 2004



	Print-Friendly Version

Jun	JUL	Nov
	20
2005	2006	2007