Tumor Marker – Part 12 – Alpha-Fetoprotein (AFP)

Alpha-Fetoprotein
- This is a glycoprotein. This consists of the single polypeptide chain and has a 4% carbohydrate.
- This is produced by the yolk sac and liver in the fetus.
- It is normal after about 18 months of birth.
- It is close to albumin, genetically, and structurally.
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- Gene coding for both is chromosome 4q.
- Its concentration is 10% that of the albumin.
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- The function of the AFP:
- Its main role is to bind and transport substances that are not water-soluble, like steroids hormones, lipids, vitamins, and bilirubin.
- Maternal serum AFP is lower than expected in the Down’s syndrome.
- Maternal serum AFP is raised or higher level in the neural tube defect.
- Level > 1000 µg/L indicate malignancy.
- At this level, 50% of the liver cell carcinomas are diagnosed.
- It is ideal to diagnose the liver tumor below the size of 5 cms.
- To find these small tumors cut-off value has to be set at a lower level between 200 to 1000 µg/L.
- In healthy individuals is 10 µg/L.
- This is a tumor marker for:
- Liver cell carcinoma. >500 ng/mL is diagnostic of liver cell carcinoma.
- Germ cell tumor (nonseminomatous tumor).
- Choriocarcinoma element in seminoma, yolk sac, teratoma, and embryonal cell carcinoma.
- AFP is useful for liver cell carcinoma:
- Diagnosing.
- Prognosis.
- Monitor therapy.
- Normal
- Adult = <40 ng/mL (<40 µg/L)
- Child <1 year = <30 ng/mL