Alpha-fetoprotein

alpha-fetoproteinAlpha-fetoprotein (AFP, α-fetoprotein; also sometimes called alpha-1-fetoprotein, alpha-fetoglobulin, or alpha fetal protein) is a plasma glycoprotein that help to transport.

Description
Alpha-fetoprotein is a globulin protein secreted by the yolk sac, gastrointestinal tract and by fetal liver cells during hepatic cell multiplication, during the adulthood in the liver. Therefore the highest amounts of AFP are found during pregnancy and in hepatic cancer and sometimes in case of other malignancies.
Although AFP is not a specific genetic marker for malignancies, its measurement may be used to monitor the effectiveness of surgical and chemotherapeutic management of hepatomas and germ cell neoplasms.
It consists of 591 amino acids and a carbohydrate moiety. The molecular mass is about 70 kDa. The gene that controls the production of AFP is located on the q arm of chromosome 4 (4q25).

Reference values
The reference values during the pregnancy are:
12 weeks’ gestation <42 µg/mL;
14 weeks’ gestation <35 µg/mL;
16 weeks’ gestation <29 µg/mL;
18 weeks’ gestation <20 µg/mL;
20 weeks’ gestation <18 µg/mL;
22 weeks’ gestation <14 µg/mL;
30 weeks’ gestation <3 µg/mL;
35 weeks’ gestation <2 µg/mL;
40 weeks’ gestation <1 µg/mL;
Normal adult levels are usually achieved by the age of 8 to 12 months.
Approximately 97 to 98% of the healthy population present AFP levels less than 8.5 ng/mL. In high risk patients, AFP values between 100 and 350 ng/mL suggest hepatocellular carcinoma. Concentrations over 350 ng/mL usually are indication of the disease.
Expected values for the AFP ELISA Test System male and female < 8.5 ng/mL (97–98%).

Indications
The test is performed when a fetal abnormality and especially defect of the neural tube in the fetus is suspected according to the results of ultrasonography examination. Between the 16 and 18th weeks of gestation AFP level is measured in a maternal serum triple or quadruple screening test. The amount of AFP in the amniotic fluid may also be measured using amniocentesis.
The test is required in case of possible liver malignancies as well as to monitor the management of hepatoma and germ cell neoplasms and To follow up patients with chronic hepatitis or liver cirrhosis.

Increased level
The level of alpha-fetoprotein in a pregnant woman may be increased in case of:
– anencephaly (the absence of a major portion of the brain, skull, and scalp that occurs during embryonic development);
– cystic fibrosis (genetic disorder);
– duodenal atresia (the congenital absence or complete closure of a portion of the lumen of the duodenum);
– esophageal atresia (the congenital absence or complete closure of a portion of the lumen of the esophagus);
– fetal bladder neck;
– obstruction with hydronephrosis;
– fetal death;
– meningomyelocele (hernial protrusion of the spinal cord and its meninges through a defect in the vertebral arch);
– multiple pregnancy;
nephrosis (congenital);
– neural tube defects;
– spina bifida (the defect of the vertebral arch);
– omphalocele (a birth defect of the abdominal wall);
– Turner syndrome (a condition in which a female is partly or completely missing an X chromosome).
– In children, adults and nonpregnant women AFP level may be increased in case of:
– ataxia-telangiectasia syndrome (neurodegenerative, autosomal recessive disease);
– hereditary tyrosinemia (enzymopathy);
– cirrhosis;
alcoholic hepatitis;
– hepatocellular carcinoma;
– primary hepatoma,
– some tumors and teratomas including yolk sac-derived tumors;
– Hodgkin’s disease (a type of lymphoma);
– lymphoma;
– renal cell carcinoma;
– viral hepatitis.

Check out the  Alpha-Fetoprotein Test.

Decreased level
Maternal serum concentrations are analyzed as an indicators of fetal trisomy of chromosome 18 (Edwards syndrome) or 21 (Down syndrome) if the level is lower than it’s supposed to be according to the gestational period.

The test
A blood sample is needed. Most of the time, blood is typically drawn from a vein located on the inside of the elbow or the back of the hand.
Measurement is usually performed from week 16 to 20 to help identify fetal abnormalities.