ALPHA-FETOPROTEIN (AFP)

CLINICAL UTILITY:

AFP is a glycoprotein which is synthesized in the fetal liver and is also present in the sera of infants and pregnant women. It is normally absent or found in very low concentration in the sera of adults and children over one year of age. An important use of measuring AFP levels has been in the detection of fetal neural tube defects. Elevated levels of protein are present in the amniotic fluid and in the sera of pregnant women in cases of open spina bifida, fetal myelocele, anencephaly and similar neuroectodermal disorders. Abnormally low concentrations in pregnancy suggest Downs syndrome.

High levels of AFP (>1000 ng/ml) are associated with approximately 70% of cases of hepatocellular carcinoma, and are also found in children with teratoblastomas of the testes and ovary. The tumor mass seems to correlate with the serum level of AFP, with levels returning to normal following surgical removal of the tumor. Therefore, serial determinations of AFP are useful in monitoring the patient during therapy or following surgery.

Increased levels (usually below 1000 ng/ml) sometimes occur in carcinomas of the pancreas, stomach, colon and lung, and in nonneoplastic hepatic diseases such as chronic active hepatitis, alcoholic cirrhosis and severe active hepatitis. Elevated levels can also occur in inflammatory and degenerative diseases such as Crohn’s disease and ulcerative colitis.

METHOD DESCRIPTION:

The serum level of AFP is measured colorimetrically using a solid phase immunoenzymatic assay (“sandwich” technique).

REFERENCE RANGE:

For amniotic fluid and maternal serum, the reference range varies with gestational age, and is reported with the test result. For more information call the lab (548-6149).

SPECIMEN REQUIREMENTS:

Amniotic fluid: 2 ml (0.5 ml minimum). Refrigerate, do not freeze.
Maternal serum: 2 ml serum (0.5 ml minimum). Refrigerate or freeze.
Non-maternal serum: 2 ml serum. Refrigerate or freeze.