Usually, the body contains very small amounts of alpha fetoprotein (AFP), but the amount of AFP in the blood increases when there is liver disease, certain malignancies, or when you are pregnant.
Increased levels of AFP do not necessarily mean that there is a health problem; some people simply have a higher than normal basal level of AFP.
Purpose of the test
Physicians ask patients to have their blood tested for AFP tumor markers primarily to:
- Find the cause of liver, testicular, and ovarian masses;
- help determine the best cancer treatment;
- observe the efficacy of cancer treatment;
- To determine if the cancer recurs after treatment.
For fetuses, AFP testing can also help predict birth defects. Sometimes, it is also possible for doctors to test for AFP in the cerebrospinal fluid.
Testing methods
The test is usually done by drawing venous blood from the arm using a syringe, either in an outpatient or inpatient setting, and the blood is then sent to a laboratory for testing.
Test results
Blood levels of AFP are measured in nanograms per milliliter (ng/mL). Most healthy adults have AFP levels of 0 to 8 ng/mL.
Many diseases can cause elevated AFP, such as cancer, liver disease (hepatitis, cirrhosis, and healing liver injury). Patients may need multiple tests to get a correct diagnosis.
Very high levels of AFP (e.g., 500 to 1000 ng/mL and higher) are often a sign of certain cancers; other types of cancer do not cause elevated AFP.
A fetoprotein higher than 200 ng/mL often means that liver cancer has occurred if there is existing liver disease.
Special AFP-L3% test
For people with elevated AFP but not more than 200 ng/mL, your doctor may need to test for the ratio AFP-L3% of the AFP heteroplasm (also called L3 AFP).
This test reflects the ratio of a specific type of AFP (AFP-L3) to the total AFP level in the blood. The results help your doctor determine your condition, especially in patients with chronic liver disease (such as cirrhosis).
An AFP-L3% test result of 10% or more indicates a high likelihood of liver cancer, and your doctor should look carefully for signs of liver cancer.
Determining treatment and recurrence
These tests also help doctors determine how well cancer treatment is working. Ideally, AFP returns to normal levels.
Regularly checking AFP can also help detect the return of cancer early. When cancer comes back, AFP can be elevated, sometimes before the patient has symptoms.