Alpha-fetoprotein (AFP)

Alpha-fetoprotein (AFP)

Indications for alpha-fetoprotein (AFP):

1. Identification, monitoring the course and effectiveness of therapy for primary hepatocellular carcinoma;
2. Monitoring the effectiveness of therapy and diagnosis of germinoma;
3. Detection of fetal malformations (neural tube defects and abdominal wall, Down's syndrome) and fetal monitoring during pregnancy.

Alpha-fetoprotein - a glycoprotein with a molecular mass of 70 kDa. In terms of composition and amino acid sequence alpha-fetoprotein is similar to albumin. During the electrophoresis alpha-fetoprotein migrates in α-globulins zone. Also alpha-fetoprotein has a high estrogen-binding capacity.

During pregnancy alpha-fetoprotein is produced by cells of yolk sac, later by the liver of the embryo, and cells of the gastro-intestinal tract of the fetus. Alpha-fetoprotein (AFP) detected in the serum of the fetus, beginning with the 4-th week of pregnancy, with maximum levels between 12-16 weeks with the peak content in 13 weeks (2-3 mg/ml). Then the level of alpha-fetoprotein in the serum of the fetus gradually decreases until the birth.

To monitor the antenatal period is important to test alpha-fetoprotein in serum and amniotic fluid of pregnant. The values of alpha-fetoprotein, significantly exceeding the level of the norm for a given gestational age indicate a neural tube defect. Abnormally low values of alpha-fetoprotein after 10 weeks of pregnancy may indicate Down syndrome.

Currently the following core functions of alpha-fetoprotein during normal development of the fetus are:

• the maintenance of the osmotic pressure of fetal blood
• protection of the fetus from mother's immune system
• the binding of estrogen contained in the mother's bloodstream
• participation in the organogenesis of liver

Normal values of alpha-fetoprotein in the serum of a healthy person does not exceed 15 ng/ml.

Elevated levels of alpha-fetoprotein detected in hepatocellular carcinomas and teratocarcinoma yolk sac of the ovary or testicles. The level of alpha-fetoprotein in serum (>1 000 ng/ml) correlated with the size of the growing tumor and the effectiveness of therapy.

Reducing the concentration of alpha-fetoprotein in the blood after removal of the tumor or the treatment to normal value serves as an auspicious sign. Re increasing the level of alpha-fetoprotein or lack of a decrease may indicate a relapse or the presence of metastases.

In malignant tumors of breast, bronchial, colorectal carcinoma in 9% of patients with metastases to the liver levels of alpha-fetoprotein is elevated, usually up to 100 ng/ml, and almost never exceeds 500 ng/ml. At the same time, in these patients a very high level of cancer embryonic antigen (CEA). Therefore, combined determination of alpha-fetoprotein and cancer embryonic antigen (CEA) helps to differentiate these pathologies with primary hepatocellular carcinoma.

Determination of alpha-fetoprotein suitable for screening of hepatocellular carcinoma in high-risk groups, especially against the background of increasing activity of enzymes such as alkaline phosphatase, γ-glutamyl transferase, glutamate dehydrogenase and aspartate aminotransferase. Elevated levels of alpha-fetoprotein also detect and hepatitis, but in these cases, the content rarely exceeds 500 ng/ml and is temporary in nature.