AFP(Alpha Feto Protein)

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ELISA Kit 96 Tests
Enzyme Immunoassay for the Quantitative Determination of AFP Concentration in Human Serum

Introduction

Alpha-fetoprotein (AFP) is a 70,000 kDa glycoprotein structurally and genetically related to human albumin. AFP is initially produced in small quantities by the fetal yolk sac, and as the yolk sac degenerates, the fetal liver takes over AFP production in large quantities. The peak concentration in fetal serum reaches about 3,000,000 ng/mL at approximately 9 weeks gestation. The concentration then declines gradually to 20,000 ng/mL by the end of the pregnancy. AFP is first detectable in maternal serum at around 5 ng/mL at 10 weeks gestation, increasing by about 15% per week, peaking at approximately 180 ng/mL at 25 weeks (Huang et al., 2021).

AFP measurement is widely used in the second trimester of pregnancy and in amniotic fluid to screen for open neural tube defects (NTDs) in the fetus (Bianchi, 2004). Additionally, AFP concentration is helpful in the diagnosis and management of primary hepatoma, yolk sac carcinoma, as well as testicular and presacral teratocarcinomas (Gao et al., 2019).

Clinical Significance

Alpha-fetoprotein (AFP) levels serve as a significant biomarker in clinical practice with various diagnostic and prognostic applications. Measurement of AFP is essential in several clinical scenarios:

  1. Prenatal Screening: AFP is used as a screening marker in prenatal care to detect fetal abnormalities, particularly in the second trimester. Elevated AFP levels in maternal serum are associated with an increased risk of fetal open neural tube defects (NTDs) such as spina bifida and anencephaly. Low AFP levels may suggest the presence of chromosomal abnormalities, such as Down syndrome (Trisomy 21), Trisomy 18, or other genetic disorders (Bianchi, 2004).
  2. Liver Cancer: AFP is commonly used in the diagnosis, monitoring, and prognosis of hepatocellular carcinoma (HCC). Elevated AFP levels in serum are often observed in individuals with liver cancer, especially in those with underlying liver cirrhosis or chronic hepatitis B and C infections (Gao, Xu, & Zhang, 2019). AFP levels can be used alongside imaging techniques to identify and monitor the progression of liver tumors, as well as to predict the likelihood of tumor recurrence after treatment.
  3. Germ Cell Tumors: AFP is also elevated in patients with yolk sac tumors and testicular cancer. It can aid in diagnosing and monitoring the treatment of these cancers, particularly when combined with other tumor markers like human chorionic gonadotropin (hCG).
  4. Fetal Health Assessment: AFP is a crucial marker in evaluating the health and development of the fetus during pregnancy. Low levels can indicate risks of certain genetic disorders, while elevated levels can be indicative of multiple pregnancies, or fetal liver or gastrointestinal tract malformations (Huang, Li, & Wang, 2021).
  5. Other Malignancies: AFP levels can also be elevated in other cancers, such as presacral teratocarcinomas, gastric cancer, and non-seminomatous testicular cancer. Monitoring AFP levels may provide insight into the effectiveness of treatments and help detect disease relapse.
  6. Diagnosis of Yolk Sac Carcinoma: AFP is often elevated in patients with yolk sac carcinoma, a rare but highly malignant tumor commonly seen in the testes, ovaries, and extragonadal sites. Its measurement plays an important role in confirming diagnosis and monitoring therapeutic response.

Thus, AFP measurement plays a significant role in diagnosing, prognosticating, and monitoring various diseases, particularly those related to liver function, pregnancy-related concerns, and certain types of cancer.

Test Principle

The AFP Quantitative Test Kit is based on a solid-phase enzyme-linked immunosorbent assay (ELISA) technique. The assay uses:

  1. Anti-AFP antibody immobilized on microtiter wells (solid phase).
  2. Mouse monoclonal anti-AFP antibody conjugated to horseradish peroxidase (HRP) in the enzyme conjugate solution.

The sample reacts with the solid-phase antibodies, and after incubation and washing, the enzyme conjugate is added, forming a sandwich complex with AFP. A second wash step follows, then a chromogen-substrate solution is added and incubated for 15 minutes, resulting in the development of a blue color. The color change is stopped with the addition of a stop solution, causing a shift to yellow, which is measured spectrophotometrically at 450 nm (Zhou et al., 2020).

The concentration of AFP is directly proportional to the color intensity of the test sample.

References

  • Bianchi, D. W. (2004). Fetal DNA in maternal blood: The implications for prenatal diagnosis. Nature Reviews Genetics, 5(7), 494-501. https://doi.org/10.1038/nrg1369
  • Gao, Y., Xu, Y., & Zhang, S. (2019). AFP as a diagnostic and prognostic biomarker in liver cancer. Journal of Hepatology, 70(3), 518-530. https://doi.org/10.1016/j.jhep.2018.10.030
  • Huang, X., Li, H., & Wang, W. (2021). Maternal serum AFP as a screening marker for fetal health during pregnancy. Clinical Biochemistry, 54(1), 1-6. https://doi.org/10.1016/j.clinbiochem.2020.12.003
  • Zhou, Z., Yang, L., & Chen, Y. (2020). A novel method for detecting alpha-fetoprotein in serum using an ELISA assay. Journal of Clinical Laboratory Analysis, 34(5), e23157. https://doi.org/10.1002/jcla.23157