Alpha-fetoprotein is a single polypeptide chain glycoprotein with a molecular weight of approximately 70,000 daltons. The physicochemical properties and amino acid composition are similar to those of albumin.
Synthesis of AFP occurs primarily in the liver and yolk sac of the fetus. It is secreted into fetal serum, reaching a peak at about 13 weeks gestation and gradually declining thereafter. Elevated serum AFP levels subsequently reappear during pregnancy and in conjunction with several malignant diseases.
Alpha-fetoprotein (AFP) was first described as a human tumor-associated protein in 1964 by Tatarinov. Since then, it has been shown that elevation of serum AFP above values typically found in healthy individuals occurs in several malignant diseases, most notably nonseminomatous testicular cancer and primary hepatocellular carcinoma. In the case of nonseminomatous testicular cancer, a direct relationship has been observed between the incidence of elevated AFP levels and the stage of disease. Elevated AFP levels have also been observed in patients diagnosed as having seminoma with nonseminomatous elements but have not been observed in patients with pure seminoma. Human chorionic gonadotropin (hCG) and AFP are also important prognostic indicators of survival rate among patients with advanced nonseminomatous germ cell testicular tumors.
The usefulness of AFP measurements in the management of patients with nonseminomatous testicular cancers has been well documented. For patients in clinical remission following treatment, AFP levels generally
decrease. Post-operative AFP values which fail to return to normal strongly suggest the presence of residual tumor. Tumor recurrence is often accompanied by a rise in AFP before progressive disease is clinically evident.
Many studies have confirmed the utility of AFP in the early detection of fetal open neural tube defects (NTD). In the US, NTD, primarily anencephaly and spina bifida, occur at the rate of between 1 and 2 per 1000 live births and are among the most common major congenital malformatlons.The Incidence of NTD varies geographically and across racial groups.Anencephaly is incompatible with life and accounts for one-third to one-half of all NTD. Open spina bifida can vary widely in severity. AFP testing during pregnancy is recommended as an effective way to determine those women potentially at risk of carrying a fetus affected with
an open NTD.
Used in conjunction with other confirmatory procedures such as ultrasonography or amniography, measurement of AFP serves as an important tool in the care and management of these patients.
Manufacturer’s Reagent package insert Architect AFP, October 2015, Abbott Ireland Diagnostics Division, Finisklin Business Park Sligo, Ireland.