AFP test explained (alpha-fetoprotein)

Alpha-fetoprotein is a protein made by the liver and by liver tumour cells. In the blood of healthy children and adults who are not pregnant there is very little of it, but some tumours — especially those of the liver (hepatocellular carcinoma), and also germ cell tumours of the ovaries or testicles — can produce large amounts of AFP, which is why it is used as a tumour marker. The AFP test is most often ordered not to make a diagnosis, but to monitor how well treatment of an already known tumour is working, to assess prognosis, or to detect a recurrence of the disease earlier than it would show up as symptoms. It is also used to monitor people with chronic liver disease (cirrhosis, chronic hepatitis B or C) who have an increased risk of liver cancer. It is important to know that AFP is not specific to cancer alone — benign liver conditions can raise it as well. For that reason the result of a single test is always assessed together with imaging (ultrasound, CT, MRI) and a doctor's examination, and not on its own as a diagnosis. The AFP test used in pregnancy to screen for fetal defects is performed differently and has different reference values — that is a separate test, not this tumour marker.

• To monitor how well treatment of an already diagnosed tumour of the liver, ovaries or testicles is working
• To assess the prognosis of the disease after a tumour has been diagnosed
• To look for signs of the tumour coming back after treatment
• To monitor people with cirrhosis or chronic hepatitis B or C, who have an increased risk of liver cancer
• When imaging (ultrasound, CT) shows a suspicious lesion in the liver

MedlinePlus (the US National Library of Medicine) does not give a general numeric AFP range, because the cut-off depends on the laboratory method and on the units used. You will find the exact reference interval of your own laboratory on your test report — it is printed together with the result.

A raised AFP

A raised AFP can be linked to liver cancer (hepatocellular carcinoma) or to germ cell tumours of the ovaries or testicles. It can also be raised by benign liver conditions — cirrhosis, chronic hepatitis B or C. A single raised result does not in itself mean a diagnosis of cancer — it is always assessed together with imaging and a doctor's examination.

What a raised AFP can be linked to

• Liver cancer (hepatocellular carcinoma)
• Germ cell tumours of the ovaries
• Tumours of the testicles
• Cirrhosis of the liver
• Chronic hepatitis B or C

• Liver imaging (ultrasound, CT or MRI) to clarify a raised result
• Liver function tests — ALT, AST, bilirubin — to assess the state of the liver
• Where a tumour has already been diagnosed — comparison with earlier AFP results over time
• A discussion with a doctor about further monitoring or additional tests

A falling AFP

A falling AFP level during treatment is usually taken as a good sign — it may mean that the treatment being given is working. According to MedlinePlus, the AFP test is used precisely for this: to monitor how well treatment is working and to notice in time if the tumour comes back, should the level rise again. A normal AFP makes an AFP-producing tumour less likely, but it does not rule out cancer — not all tumours produce AFP (MedlinePlus).

• The cancer treatment being given is working — according to MedlinePlus, a falling AFP during treatment may mean that the treatment is effective
• The tumour is shrinking — according to MedlinePlus, the AFP level often falls when the tumour shrinks

What is usually done next: a comparison with earlier results, to judge the trend of the treatment, and repeat testing at regular intervals on the schedule set by the doctor, to watch for a possible recurrence.

AFP in pregnancy is a different test

There is a separate AFP test used during pregnancy to assess the risk of neural tube defects in the fetus or of genetic disorders — it differs from this tumour marker test and has different reference values and different rules of interpretation.

Related pages: beta-hCG, ALT and how to read blood test results.