α-fetoprotein (AFP)
Why this test?
- For prenatal diagnosis of pathologies of fetal development: neural tube defects, anencephaly (severe malformation in which the fetus is missing part of the brain), chromosomal abnormalities.
To detect primary hepatocellular carcinoma (liver cancer). - To detect testicular teratoblastoma (germinogenic non-seminoma).
- For the diagnosis of poorly differentiated tumors.
- For the diagnosis of metastases of tumors of various localizations in the liver.
- To evaluate the effectiveness of treatment of some oncological diseases and to monitor their progress.
In what cases is it prescribed?
When examining a patient with a high risk of tumor development (with liver cirrhosis, chronic hepatitis, alpha-antitrypsin deficiency).
In case of suspicion of metastasis of tumors in the liver.
When examining a patient with a neoplasm of the gonads.
Before, during and after treatment of certain cancers.
When observing the condition in the postoperative period of patients from whom the tumor was removed. In the second trimester of pregnancy (between the 15th and 21st weeks of gestation).
When examining pregnant women who underwent amniocentesis and chorionic biopsy in the early period of pregnancy.
Test information
Alpha-fetoprotein is a glycoprotein produced in the embryonic yolk sac, liver and intestinal epithelium of the fetus. The molecular weight of the protein is about 70,000 daltons, its half-life is 5-7 days. In the body of the fetus, it performs the functions of albumin of an adult: it carries out the transport of some substances necessary for the development of the fetus, binds estrogens, limiting their impact on the developing body, and protects against the negative effects of the mother's immune system. Alpha-fetoprotein takes an active part in the full development of the fetus, and its level should correspond to gestation (the age of the fetus from the moment of fertilization).
The maximum content of this protein in the blood and amniotic fluid of the fetus is noted at the 13th week, and in the blood of the mother it gradually increases from the 10th week of pregnancy and reaches a maximum at 30-32 weeks. 8-12 months after birth, the content of AFP in the child's blood decreases to trace amounts, as in adults. Alpha-fetoprotein enters the mother's body through the placenta. Its level depends on the state of the gastrointestinal tract, fetal kidneys and placental barrier. In this regard, AFP is used as a non-specific marker of fetal condition and obstetric pathology. Joint tests for AFP, chorionic gonadotropin and estriol (so-called triple test) at 15-20 weeks of pregnancy are used to check the fetus for developmental defects and chromosomal abnormalities, but are not absolute indicators of pathology or normal fetal development.
At the same time, it is very important to know exactly the gestational age of the fetus, since the level of AFP in the blood differs in different weeks of pregnancy. Alpha-fetoprotein is absent or found in minimal amounts in the body of an adult. A moderate increase in its level can be caused by liver pathology, and a significant one - by a poorly differentiated tumor - this is due to the fact that some cancerous neoplasms acquire the properties of embryonic tissues and, accordingly, the ability to synthesize proteins, which are characteristic of the early stages of the body's development.
A sharp increase in AFP is mainly found in cancer of the liver and gonads. In primary hepatocellular carcinoma, an increase in AFP can be detected in half of patients 1-3 months before clinical manifestations of the disease. Although the size of the tumor, the intensity of growth, the stage of the process and the degree of malignancy are not proportional to the amount of alpha-fetoprotein in the blood. With progressive germinogenic non-seminoma (tumor of the gonads), determining the level of AFP and chorionic gonadotropin is important for assessing the chances of survival of patients.
