Alpha-Fetoprotein (AFP) Blood Test

  • Medical Author:
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

  • Medical Editor: Charles Patrick Davis, MD, PhD
    Charles Patrick Davis, MD, PhD

    Charles Patrick Davis, MD, PhD

    Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

What is the alpha-fetoprotein (AFP) blood test?

The most abundant plasma protein found in the human fetus is alpha-fetoprotein (AFP). AFP is a protein normally made by the immature liver cells in the fetus. At birth, infants have relatively high levels of AFP in the blood, which fall to normal low adult levels by the first year of life. Also, pregnant women carrying babies with neural tube defects may have high levels of AFP in both the bloodstream and in the amniotic fluid. A neural tube defect is an abnormal fetal brain or spinal cord that is caused by folic acid deficiency during pregnancy. Alpha-fetoprotein is also produced by certain cancers and is sometimes measured as a tumor marker. The AFP tumor marker test requires a blood sample. Other names for the test include total AFP and alpha-fetoprotein-L3 percent (%).

In which situations are high blood levels of AFP seen in adults?

In adults, high blood levels (over 500 nanograms/milliliter [or ng/ml]) of AFP are seen in only a few situations, such as

  1. hepatocellular carcinoma (HCC), a primary cancer of the liver;
  2. germ cell tumors (a type of cancer of the testes and ovaries);
  3. ataxia telangiectasia, a severely disabling and rare genetic neurodegenerative disease; and
  4. less commonly, in other types of cancer, including lymphoma or cancer of the lung, breast, or colon.

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What tests are available for measuring AFP?

Several assays (tests) for measuring AFP in the blood are available. Generally, normal levels of AFP are below 10 ng/ml. Patients with various types of acute and chronic liver diseases without documentable liver cancer can have mild or even moderate elevations of AFP, though usually less than 500 ng/ml.

An AFP test is usually not done at home or a doctor's office; it is usually done in a hospital lab or a reference lab.

The use of the AFP assay in prenatal, perinatal, and pediatric care is beyond the scope of this discussion. We will confine the discussion to its use as a tumor screening test and as a tumor marker.

What is the sensitivity of AFP for diagnosing liver cancer?

Primary liver cancer, or hepatocellular carcinoma or hepatoma, is more common in some forms of chronic liver disease. As a screening test in patients with chronic hepatitis B and C, or hemochromatosis, AFP has a sensitivity for liver cancer of about 60%. In other words, an elevated AFP blood test is seen in about 60% of liver cancer patients. That leaves 40% of patients in these high-risk groups who can have liver cancer but have normal AFP levels. Consequently, the test is not diagnostic but is an indicator of a potential situation. Therefore, a normal AFP does not exclude liver cancer. For example; AFP levels are normal in a fibrolamellar carcinoma, a variant of hepatocellular carcinoma. Also, as noted above, an abnormal AFP does not mean that a patient has liver cancer. It is important to note, however, that patients with cirrhosis and an abnormal AFP, despite having no documentable liver cancer, still are at very high risk of developing liver cancer. Thus, any patient with cirrhosis and an elevated AFP, particularly with steadily rising blood levels, will either most likely develop liver cancer or actually already have an undiscovered liver cancer.

An AFP greater than 500 ng/ml is very suggestive of liver cancer. In fact, the blood level of AFP loosely relates to (correlates with) the size of the liver cancer.

Finally, in patients with liver cancer and abnormal AFP levels, the AFP may be used as a marker of response to treatment. For example, an elevated AFP is expected to fall to normal in a patient whose liver cancer is successfully removed surgically (resected). If AFP then increases again, liver cancer recurrence is likely.

In non-seminomatous germ cell cancers of the testis, the AFP is measured at diagnosis, and followed as a tumor marker in a fashion similar to that described above in resected hepatocellular carcinoma patients.


United States. National Cancer Institute. "Tumor Markers." Nov. 4, 2015. <>.

University of Rochester Medical Center. "Alpha-Fetoprotein Tumor Marker (Blood)." <>.

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Reviewed on 6/14/2016

United States. National Cancer Institute. "Tumor Markers." Nov. 4, 2015. <>.

University of Rochester Medical Center. "Alpha-Fetoprotein Tumor Marker (Blood)." <>.

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