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What is AFP (Alpha Feto Protein) test?

AFP test stands for alpha-fetoprotein test. Alpha-fetoprotein is synthesised by liver cells in an adult and growing foetus.

In an adult, the levels of AFP in blood are usually undetectable but they tend to rise in the presence of certain types of tumours. Hence, the presence of AFP in the blood of an adult person can be an indication of a developing tumour. Different levels of AFP can be associated with various stages of tumour growth. Therefore, AFP also acts as a tumour marker.

Since AFP is produced by the regenerating cells of liver, a change in its blood levels over time can also be an indication of liver diseases or dysfunction.

AFP produced by foetus keeps on entering maternal blood circulation, its levels increase through the second trimester and reach maximum levels in the mother’s blood. Since an adult originally does not have detectable levels of AFP in their blood, checking its levels in maternal circulation can help diagnose medical conditions associated with increased AFP in foetus.

  1. Why is AFP Test performed?
  2. एएफपी ब्लड टेस्ट क्यों किया जाता है? - What is the purpose of Alpha Fetoprotein Test?
  3. एएफपी ब्लड टेस्ट के दौरान - During Alpha Fetoprotein test in Hindi
  4. एएफपी ब्लड टेस्ट के बाद - After Alpha Fetoprotein Test in Hindi
  5. एएफपी ब्लड टेस्ट के क्या जोखिम होते हैं? - What are the risks of Alpha Fetoprotein Test in Hindi?
  6. What do AFP test results mean?
  7. How is AFP test performed?
  8. How do you prepare for AFP test?

A healthcare practitioner would order for an AFP test under the following circumstances:

An AFP test is done as part of the standard screening procedure for pregnant women in the second trimester, especially those 35 years and above.

AFP test results can help corroborate the results of some tests when an individual has inconsistent symptoms that are undiagnosed by other tests. AFP levels can help the diagnosis of conditions such as:

  • Metabolic disorders in children
  • Chronic hepatitis and jaundice
  • Liver tumour
  • Testicular malignancy
  • Tumours in infants and children
  • Developmental defects in foetus, e.g., spina bifida
  • Down syndrome detection in the growing foetus
  • Chromosomal abnormalities in  foetus
  • Tumours of  ovaries, stomach and central nervous system

Normal results:

In men and non-pregnant women, typically there is no AFP or low levels of AFP in the blood; results vary in a range of 0-40 ng/mL.

In pregnant women, AFP usually rises in the second trimester, from week 14 to 32. AFP test is performed around the 16th week, where the levels typically are in the range of 10-150 ng/mL. These values indicate that the foetus is developing normally.

New-born babies and infants up to 1 year can also have higher levels of AFP, which are considered normal.

Abnormal results:

In men and non-pregnant women, increased values of AFP could be indicative of the following conditions:

  • Liver tumour: When test values are higher than 200 ng/mL and the individual is also suffering from liver cirrhosis or hepatitis, liver tumour is a possibility. Values greater than 500 ng/mL in a person who does not have cirrhosis or hepatitis also indicate the presence of a tumour.
  • Testicular or ovarian tumours: When liver function tests show normal results, but AFP levels are high.
  • Liver dysfunction: This needs to be correlated with other liver function tests to confirm diagnosis.
  • Paediatric tumours: If AFP levels continue to be high even after 1 year of age in infants.

In pregnant women, abnormal results of  AFP test could indicate the following:

  • High AFP values
    • Conception of twins
    • Neural tube defects in foetus, for example, anencephaly (the baby is missing a major portion of the brain or skull)
    • Developmental defects, such as omphalocele (the baby’s abdominal organs are outside the body through a hole in the belly button area)
    • Obstetric complications
  • Low AFP values
    • Down syndrome or Trisomy 21

False positives with AFP testing in a pregnant woman can also occur when the gestation period is miscalculated or the woman has gestational diabetes. It is essential that the results of AFP test should be examined by a doctor so that other diagnostic tests may be advised, if required, for an accurate diagnosis.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.

For all individuals undergoing AFP test, a sample of blood is collected from the upper arm using a sharp needle after swabbing the concerned area with appropriate antiseptic. One might experience minor pain with needle insertion, which will disappear soon. A technician will place the blood sample in a sterile vial, which is then sent for the test.

Some patients may experience mild bruising on the skin due to needle prick; however, it will fade within some time.

In case of inconsistent results, the doctor may advise testing urine or amniotic fluid for AFP.

AFP test is typically a blood test that does not require much preparation. Individuals going through this test must keep their doctor informed about all medicines and herbal supplements they may be taking. Also, they must inform the doctor about a smoking habit, status of pregnancy, the possibility of conception of twins or any medical condition they may have. Do not change the course of any medication without the consent of the doctor.

References

  1. University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; Alpha-Fetoprotein Tumor Marker (Blood)
  2. Marshal W.J, Lapsley M, Day A.P, Ayling R.M. Clinical biochemistry: Metabolic and clinical aspects. 3rd ed. Churchill Livingstone: Elsevier; 2014. Chapter 14, Acute and chronic liver disease; p.263-267
  3. Adigun O.O, Khetarpal S. Alpha Fetoprotein (AFP, Maternal Serum Alpha Fetoprotein, MSAFP). Treasure Island (FL): Stat pearls Publishing, 2019
  4. Gerard J. Tortora, Bryan Derrickson. Principles of anatomy and physiology. 14th ed. Wiley Publication; 2014. Chapter 29, Development and Inheritance; p.1110-1111.
  5. American Cancer Society [internet]. Atlanta (GA), USA; Can Liver Cancer Be Found Early?
  6. Johns Hopkins Medicine [Internet]. The Johns Hopkins University, The Johns Hopkins Hospital, and Johns Hopkins Health System; Liver Cancer Diagnosis at Johns Hopkins
  7. American Pregnancy Association: Maternal Serum Alpha-Fetoprotein Screening (MSAFP)