Generality
Alpha-phetoprotein (AFP ) is a glycoprotein substance with functions similar to those of albumin, synthesized above all during fetal life from the yolk sac and the liver.
After birth, alpha-fetoprotein levels begin to fall significantly, reaching - within 12/24 months - the characteristic values of healthy adults (less than 5 ng / mL).
Specifically, alpha-fetoprotein is known to be one of the most important markers of liver cancer (hepatocarcinoma), although in this sense its specificity is certainly not optimal.
What's this
Alpha-phetoprotein is a tumor "marker", that is one of those substances that can be found in increased quantities - in the blood, urine or other body fluids - in the presence of some neoplastic processes.
The AFP is found in the maternal serum - hence its name - from the fourth week of pregnancy. In particular, this glycoprotein is produced by the developing fetus in its own liver, in the yolk sac and in the gastrointestinal tract. The AFP reaches a peak in maternal blood at the 13th week of gestation, then gradually decreases in the following months.
Immediately after birth, the newborn AFP stabilizes on an adult's normal level and always remains low, except in the case of pregnancy, liver disease or some cancers .
Why do you measure
The test measures the concentration of alpha-fetoprotein (AFP) in the blood. In healthy children and adults, AFP is normally present in very small quantities.
High concentrations of alpha-fetoprotein may be produced by certain types of liver, testis and ovarian cancer . This characteristic makes the protein useful as a tumor marker in supporting the diagnosis of these neoplastic processes.
The parameter is also useful for monitoring the progress of chronic liver diseases, such as cirrhosis, hepatitis B and hepatitis C.
When is the test prescribed?
Liver damage and some neoplastic processes can significantly increase AFP concentration. The doctor may request this analysis, along with other diagnostic imaging tests, to try to discover liver cancer when it is still in its early stages and can be treated.
The alpha-fetoprotein examination is indicated as a support for the diagnosis of hepatic, testicular and ovarian tumors . In the presence of one of these neoplastic diseases, the test is prescribed at regular intervals as an aid in monitoring during or after treatment.
The AFP test can also be recommended in the presence of cirrhosis or chronic hepatitis . In fact, alpha-fetoprotein is produced whenever the liver cells are regenerated. For this reason, AFP is consistently high in chronic liver disease.
To remember
The AFP test is not diagnostic, but provides an indication of the possibility of developing a liver tumor. For this reason, the exam must be supplemented with other information from the study of clinical history, from the patient's medical examination and from the use of imaging techniques.
Furthermore, alpha-fetoprotein may increase temporarily whenever the liver is damaged and regenerated; finally, moderate increases can be observed in many pathological and physiological conditions.
Precisely for this reason, the exam can give rise to false positive results. In addition, not all tumors produce this marker, so an individual may be suffering from cancer even if the concentration of alpha-fetoprotein is normal.
Normal values
Typically, a healthy adult has a serum alpha-fetoprotein concentration of less than 10 ng / mL.
The finding of levels higher than 500 ng / mL constitutes a rather probable diagnosis of hepatocarcinoma, as such high values are almost never observable in other pathologies (except germ cell tumors or with liver metastases).
Alphafetoprotein monitoring can also be useful as a screening test for an early diagnosis in a population at high risk of liver cancer, although its values tend to be already high in patients with chronic liver disease. Furthermore, in the post-operative period or after other therapeutic interventions, the alpha-fetoprotein dosage becomes very useful to recognize a possible relapse.
High Alphafetoprotein - Causes
High concentrations of alpha-fetoprotein are found in most people with hepatocellular carcinoma. This marker is also indicative of the presence of hepatoblastoma, a type of liver cancer that affects children.
The values of alpha-fetoprotein increase in the presence of liver diseases, such as:
- Hepatic cirrhosis;
- Acute and chronic viral hepatitis;
- Alcohol hepatitis.
Increased amounts of AFP may indicate the presence of germ cell cancer in the testes or ovaries (teratocarcinoma).
Furthermore, AFP levels can be high in the event of conditions and factors unrelated to liver disease, including:
- Carcinoma of the colorectal, stomach, pancreas or lungs;
- lymphoma;
- Taking contraceptives;
- Physical exercise;
- Chronic lung disorders.
High levels of alpha-fetoprotein also occur during pregnancy and tend to increase further if the fetus has neural tube closure defects such as spina bifida .
Low AFP - Causes
The values of alpha-fetoprotein may be low in case of:
- Gestational age lower than expected (when the date of conception is not known exactly);
- Abortion not yet identified.
In pregnant women who are carriers of fetuses with Down syndrome, serum rates of alpha-fetoprotein and non-conjugated estriol tend to decrease, while those of human chorionic gonadotropin and inhibin A increase.
How to measure it
The alpha-fetoprotein test is a laboratory analysis that involves performing a simple blood sample from a vein in the arm.
Preparation
For AFP analysis, fasting for at least 8 hours is required, to prevent food from interfering with the result.
Interpretation of Results
- Increased concentrations of AFP may indicate the presence of a tumor, among which the most common is hepatic carcinoma, but also ovarian and testicular cancer. High protein concentrations can also be observed in other diseases, such as cirrhosis and hepatitis.
- When alpha-fetoprotein is used in monitoring, decreased concentrations may indicate a good response to therapy. If the concentration does not decrease after therapy, reaching normal or close to normal, it means that the tumor tissue may still be present.
- If the AFP concentration starts to increase again, then it is likely that it is a recurrence (reappearance of the tumor).
- It is important to remember that not all liver, ovarian or testicular tumors produce significant amounts of AFP. If the concentration of this marker is not high before starting the treatment, then the test will not be useful in monitoring the efficacy of the therapy or the occurrence of recurrences.
