What is being tested?
AFP is a protein produced by fetal tissue (especially the liver) and by tumors. Increased amounts of AFP are found in the vast majority of patients with a type of liver cancer called hepatocellular carcinoma. They are also found in some patients with cancer of the testes and ovaries.

AFP exists in several different variants. Traditionally when a doctor orders an AFP test, he is ordering a total AFP, one that measures all of the AFP variants together. This is the primary AFP test in the United States.

One of the variants is called L3 because of its ability, in the laboratory, to bind to a particular protein called Lens culinaris agglutinin. The AFP-L3% test is a new test that compares the amount of total AFP to the amount of AFP-L3. An increase in the percentage of L3 to total AFP is associated with increased risk of developing hepatocellular carcinoma in the near future and of having a poorer prognosis, as the L3-related cancers tend to be more aggressive. The AFP-L3% test is being ordered by a few doctors in the U.S. and is in wider use in some other countries, such as Japan.

How is the sample collected for testing?
A blood sample is taken by needle from a vein in the arm.