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Alpha fetoprotein in the blood
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Alpha fetoprotein is a-glycoprotein, normally synthesized in the yolk sac of the embryo and then liver of the fetus. The level of alpha-fetoprotein is elevated in newborns and, therefore, in pregnant women. The content of alpha-fetoprotein decreases rapidly during the first year of life, reaching a characteristic adult level by 1 year (normal <20 ng / ml).
Reference values of α-fetoprotein in serum: adults - up to 10 IU / ml; in women in the II-III trimester of pregnancy - 28-120 IU / ml; Newborns in the first day of life - up to 100 IU / ml. Half-life is 3-6 days.
The detected increases (> 500 ng / ml) in high-risk patients (for example, when volume formation in the liver are detected with ultrasonography) is a diagnostic sign of primary hepatocellular carcinoma (HCC), although not all hepatocellular carcinomas produce alpha-fetoprotein.
Determination of alpha serum fetoprotein content is used
- for diagnosis and monitoring of treatment of hepatocellular carcinoma;
- for the diagnosis of germ cell tumors;
- To diagnose metastases of any tumor in the liver;
- for screening in high-risk groups (liver cirrhosis, hepatitis, α 1 -antitrypsin deficiency );
- for prenatal diagnosis (malformations of the nerve canal, Down's syndrome in the fetus);
- to assess the degree of maturity of the fetus.
The causes of increased alpha-fetoprotein
Since small levels of alpha-fetoprotein may be present in small tumors, an increase in alpha-fetoprotein indicates the possibility of hepatocellular carcinoma. However, the degree of increase in alpha-fetoprotein has no prognostic significance. In populations where chronic hepatitis B and hepatocellular carcinoma are common (for example, in sub-Saharan Africa, in ethnic Chinese), alpha-fetoprotein can reach very high values (for example, 100,000 ng / ml), whereas in regions with a lower incidence of the tumor, lower values are recorded (approximately 3000 ng / ml).
Some other diseases (eg, embryonic teratocarcinoma, hepatoblastoma, some liver metastases from the tumor in the gastrointestinal tract, some cholangiocarcinomas ) cause an increase in alpha-fetoprotein 500 ng / ml. With fulminant hepatitis, alpha-fetoprotein can sometimes rise to 500 ng / ml; less significant increases occur in acute and chronic hepatitis. These elevated values probably reflect liver regeneration . Thus, the sensitivity and specificity of alpha-fetoprotein varies significantly depending on the population, but the values of 20 ng / ml occur at a frequency of 39 to 64% and 76 to 91%, respectively. Since an increase in the level of alpha-fetoprotein <500 ng / ml is not a specific sign, the value of 500 ng / ml is taken as a threshold diagnostic criterion.
Alpha fetoprotein as a cancer marker has the following clinical applications: first, to identify and monitor primary hepatocellular carcinoma, which occurs, as a rule, in cirrhosis of the liver; second, to identify teratoblastoma of the testicle and, third, to evaluate the effectiveness of therapy for these diseases. Increase in the concentration of α-fetoprotein in hepatocellular liver cancer in 50% of patients is revealed 1-3 months earlier than clinical signs of the disease appear. In primary liver carcinoma, the concentration of alpha fetoprotein in the blood of more than 15 IU / ml is detected in 95% of cases (15-100 IU / ml in 12%, 100-1000 IU / ml in 14%, 1000-10 000 IU / in 29%, 10 000-100 000 IU / ml - in 39% of cases). With metastatic liver damage, the concentration of α-fetoprotein exceeds 15 IU / ml in 9% of cases (15-100 IU / ml in 7%, 100-1000 IU / ml in 2%).
The content of alpha fetoprotein correlates well with the effectiveness of chemotherapy treatment of carcinoma (a significant decrease indicates therapeutic effectiveness). Due to the fact that the full effect of chemotherapy is usually absent, normalization of the level of alpha fetoprotein in the blood of patients is not observed. Removal of the tumor is accompanied by a sharp decrease in the content of alpha fetoprotein in the blood, the persistent increase in it indicates a non-surgical treatment.