Alpha-fetoprotein (AFP)

What it measures

AFP is a protein made by the fetal liver and yolk sac. In adults it is a tumour marker for hepatocellular carcinoma and non-seminomatous germ-cell tumours; in pregnancy it is part of prenatal screening.

Specimen and preparation

• Specimen: Serum or lithium-heparin plasma
• Tube: Gold top

Reference range

Reference ranges differ between laboratories, methods and populations. Always use the range printed on your own lab report.

Causes of high values

• Hepatocellular carcinoma
• Yolk sac and non-seminomatous germ-cell tumours
• Chronic hepatitis and cirrhosis (moderate)
• Pregnancy; neural tube defects in fetus (high maternal AFP)
• Ataxia–telangiectasia

Causes of low values

• Down syndrome pregnancy (low maternal AFP)

Method

Chemiluminescent immunoassay

Good to know

Pure seminoma does not produce AFP. Levels above 400 ng/mL in a cirrhotic liver mass strongly suggest HCC.

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