AFP (Alpha-Fetoprotein) Test: What the Results Mean
The blood test is done for multiple reasons
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Medically reviewed by Steffini Stalos, DO
AFP (alpha-fetoprotein) testing is a blood test done during pregnancy to assess the fetus's risk of birth defects or genetic abnormalities. Outside of pregnancy, an AFP test will evaluate and monitor certain cancers—like liver cancer and ovarian or testicular tumors.
This article will cover AFP test results in and outside of pregnancy, what the results mean, and what other tests may be necessary.
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AFP Blood Test to Assess Birth Defects
An AFP blood test is done during pregnancy to assess the fetus's risk of developing certain conditions. The test results cannot diagnose birth defects or conditions. Abnormal test results indicate an increased risk and additional testing is necessary. It is a part of the quad screen, a group of blood tests that provide information about the fetus's health.
AFP is a protein made by the fetus. It moves from the placenta to the pregnant person's blood. An AFP test will show if the fetus has low, normal, or high levels of AFP.
Here is what the levels could mean:
Low levels of AFP mean that the fetus may have Down syndrome (trisomy 21) or Edwards syndrome (trisomy 18). Both of these conditions are chromosomal abnormalities.
High levels of AFP mean that the fetus may have a neural tube defect or abdominal wall defect. Neural tube defects are birth defects where the fetus' brain or spine does not develop properly. Spina bifida and anencephaly are two types of neural tube defects. Birth defects that affect abdominal wall formation are omphalocele and gastroschisis.
What Is a Normal AFP Test Result During Pregnancy?
The normal range of an AFP test result between 15 to 20 weeks of pregnancy is 10 to 150 nanograms (ng) per milliliter (mL) (ng/mL).
Test results will vary based on a person's age, health history, and gender. If the results fall outside the normal range, a healthcare provider can help clarify the reason and if follow-up testing is necessary.
AFP levels rise and fall at certain times during pregnancy. Therefore, it is important to have the test taken in the correct time range (between 15 and 20 weeks of pregnancy).
A high or low result could be a sign that:
The developing fetus is at high risk for a genetic condition or birth defect.
The pregnant person's estimated due date is incorrect, and as a result, the AFP test was taken at the wrong time. This is the most common cause of an abnormal AFP test result.
The pregnant person is pregnant with multiple fetuses. Each fetus makes AFP, so the amount in the pregnant person will be higher with more than one fetus.
AFP Blood Test to Assess Tumor Risk
AFP is a protein made by an unborn fetus. After birth, AFP levels drop significantly and healthy adults have very low AFP levels.
In nonpregnant people, AFP is used as a tumor marker. Tumor markers are higher in people who have certain types of cancer.
High AFP levels indicate a risk of liver cancer or an ovarian or testicular tumor. It also could be a result of noncancerous liver disease.
Takeaway
High AFP levels cannot be used as a diagnosis for cancer. AFP levels can also be normal in people who do have liver, ovarian, and testicular cancer.
What Happens During AFP Test to Assess Tumor Risk
An AFP test is performed in a lab by a healthcare provider. The healthcare provider will use a small needle to draw a blood sample from a vein in the arm. The blood is then placed into a collection tube. The blood draw should take less than five minutes.
After the blood sample is drawn, the blood is processed in a lab. The AFP test results will be provided to the healthcare provider and patient. How long it takes to process results will vary from location to location.
Learn More: Understanding Common Blood Tests and What They Mean
Other AFP Test Uses
The AFP blood test can be used to detect certain types of cancer. It can also be used for the following reasons:
Monitor the effectiveness of cancer treatment
Anticipate how cancer can change over time
Monitor if the cancer has come back after treatment
AFP testing may be done for noncancerous liver conditions like hepatitis or cirrhosis to watch the progress of the conditions.
AFP Tumor Marker Test
In a healthy adult, a normal AFP test is 0 ng/mL to 40 ng/mL. Very high results of over 400 ng/mL could indicate a liver tumor. It could also be a sign of other liver conditions or ovarian or testicular tumors.
Test results can vary from person to person and need to be interpreted along with other data. A healthcare provider will order additional testing to help determine the issue.
Follow-Up Tests After AFP Test
If someone has an abnormal pregnancy AFP result, their healthcare provider may order additional testing. These tests include:
Ultrasound: Noninvasive test that provides images of the fetus
Amniocentesis: A test of the amniotic fluid that surrounds the fetus
Noninvasive prenatal screen: A blood test to confirm a fetal genetic abnormality
Other tests that may be performed along with an AFP tumor marker test are:
Liver function tests (LFTs): This blood test examines how the liver works.
Blood-clotting tests: The liver plays a crucial role in the body's ability to make blood-clotting factors. These tests will monitor if there are any changes in how well the liver is making these factors.
Complete blood count (CBC): This blood test looks at several blood cells, including white blood cells (WBCs) and red blood cells (RBCs).
Viral hepatitis: A blood test that looks for hepatitis B and C, which are linked to liver cancer.
Tissue biopsy: A small piece of tissue is taken from an organ or mass for anatomic pathologists to further evaluate.
A healthcare provider may order other testing, like a computed tomography (CT) scan or magnetic resonance imaging (MRI) to examine the concerns. These tests would provide images of the areas to guide the provider's decision-making.
Summary
AFP testing is done during pregnancy to determine if the fetus is at risk for certain conditions or birth defects. When the test is done outside of pregnancy it is used to evaluate the liver function and determine the risk of having liver cancer or an ovarian or testicular tumor. The AFP test is a reasonable risk indicator but cannot diagnose a disease or condition. If necessary, a healthcare provider will order additional testing to make a firm diagnosis.
