The AFP test or Alpha fetoprotein test is a test that is conducted in adults and children for completely different reasons. In adults, AFP should exist in only trace amounts and therefore, if it is present in high amounts, it would indicate that there is some kind of tumor in the body. The AFP test is a tumor marker for germ cell tumors like hepatocellular carcinoma. This test is ordered when there are signs of liver disease like jaundice and but the causes are mysterious and not related to alcoholism or viral hepatitis. In fetuses the test is used to check for the possibility of a child being born with fatal errors of development and Down’s syndrome.
AFP or alpha fetoprotein is the fetal equivalent for human serum albumin. In our bodies, the carrier of materials is the blood but this blood is largely water based. This means that there is no way that lipid substances can travel through it by mixing with the blood. This is not viable because we need fat and lipid substances like cholesterol to survive. Therefore, there are a group of proteins like albumin and lipoproteins that absorb fat and lipids in their inner, swell up like bubbles, and travel in the blood stream. They are then sent to where the substances need to be. In fetuses the same principle applies but the young liver is not able to make albumin so AFP is the substitute that is made in the yolk sac of a developing embryo and eventually in the developing liver of the fetus. As a fetus grows, the levels of AFP peak in the first trimester and maintain that level. After birth, the levels of AFP remain but start to reduce to adult levels after a year of life when the liver is able to correctly make albumin.
The levels of AFP play a major role in disease of the fetus. When the levels of AFP are too low then it is a sign of Down’s syndrome. High levels are associated with more serious problems like spina bifida, the fetus not being born with a brain, parts of the brain missing, and even with the fusion of the head and chest, scalp and spine. The test for AFP can be done using amniocentesis – a method of checking amniotic fluid or by checking maternal serum levels of AFP. When a positive result ensues, the parents need to be ready to deal with the possibility of Down’s syndrome.