An AFP tumor marker test is a blood test that determines the amount of AFP (alpha-fetoprotein) in a blood sample. It is used to aid in the diagnosis of certain types of cancer and to assess how well treatment is working. AFP is a protein produced by the liver when its cells divide and grow to form new cells. AFP levels in unborn babies are typically high, but drop dramatically after birth. There is very little AFP in the blood of healthy children and adults who are not pregnant.
In non-pregnant people, AFP is primarily measured as a tumor marker. Tumor markers are substances that cancer cells or normal cells produce in response to cancer. High levels of AFP might indicate liver, ovarian, or testicular cancer, or cirrhosis or non-cancerous liver issues. An AFP tumor marker test cannot be used to screen for or diagnose cancer on its own. This is because other conditions, such as non-cancerous liver diseases, can cause an increase in AFP levels. Surprisingly, some people with liver, ovarian, or testicular cancer will have normal AFP levels. As a result, an AFP tumor marker test cannot definitively rule out cancer. However, when combined with other tests, an AFP tumor marker test can aid in the diagnosis and monitoring of certain health issues.