What is the normal value of AFP?

The liver is an important organ in the human body. When the liver is abnormal or damaged, in addition to judging by symptoms, some professional examinations are still needed. AFP refers to alpha-fetoprotein. If there is a tumor in the liver, the clinical indicator AFP should also be checked. AFP also has a normal value to measure whether the liver has abnormal performance. The normal values ​​for men and women are also different. So what is the normal value of AFP?

The normal value of AFP by enzyme-linked immunosorbent assay is ≤25μg/L. The most commonly used quantitative test is radioimmunoassay (normal value is 0-25ug/L). If it exceeds 25ug/L, it is positive. If it is between 25 and 400ug/L, it is a low-concentration positive. If it exceeds 400ug/L, it is a high-concentration positive.

Human AFP belongs to α-globulin, and its electrophoretic movement is between albumin and globulin. Its molecular weight is about 64,000-72,000, and its sedimentation coefficient is 4.5. This protein is composed of about 18 amino acids, and carbohydrates account for about 4%. AFP from the fetus exhibits consistent electrophoretic movement, while that from the tumor contains four variants or subcomponents with slightly different electrophoretic movements. This difference lies mainly in the carbohydrate content rather than in changes in the peptide chains.

Alpha-fetoprotein (α-fetoprotein, αFP or AFP) is mainly synthesized in the fetal liver, with a molecular weight of 69,000. At 13 weeks of fetal development, AFP accounts for 1/3 of the total plasma protein. It reaches its peak at 30 weeks of gestation and then gradually decreases. The plasma concentration at birth is about 1% of the peak, about 40 mg/L, and is close to the adult level (less than 30 μg/L) at one year old.