Alpha-fetoprotein (AFP) is a protein normally produced by the fetus. After birth, blood level of AFP drops rapidly and remains low. It increases in the mother’s blood during pregnancy. The measurement of AFP in adulthood is used primarily as a tumour marker (a substance found naturally in the body that may indicate the presence of cancer if its levels are high) and in combination with other tests in screening for trisomy in early pregnancy. The results are expressed in micrograms of AFP per litre of blood (µg/L).
An increase in AFP in a non-pregnant person may indicate the presence of liver, testicular or ovarian cancer. Combined with imaging tests, this test can detect these cancers at an earlier stage in order to initiate treatment more quickly. It may also be requested periodically to monitor treatment response and assess recurrence. High levels of AFP are also found in patients with non-cancerous liver diseases (viral hepatitis, cirrhosis, etc.), individuals with gastrointestinal tumours and in several benign conditions. A positive AFP test result is not a cancer diagnosis.
Results may vary from laboratory to laboratory depending on the testing technique used. If followed up, it is advisable to have the tests performed in the laboratory that produced the initial result.