Alpha-Fetoprotein Testby Alexa Lovely Fitness trainer Definition
The alpha-fetoprotein (AFP) test is a blood test that is performed during pregnancy to screen the fetus for certain conditions; it is also used to screen for certain diseases in infants and children. The screening test measures the level of AFP in the mother's blood and indicates the probability that the fetus has one of several serious birth defects. The level of AFP can also be determined by analyzing a sample of amniotic fluid.
This screening test cannot diagnose a specific condition; it only indicates the increase of risk for several birth defects. In infants and children, the AFP test is used to detect liver disease, certain cancerous tumors, and to monitor the progress of cancer treatment.
Alpha-fetoprotein is a substance produced by the liver of a fetus, by tumors of the liver, by testes and ovaries, and by certain other diseases of the liver. The exact function of this protein was as of 2004 unknown. After birth, the infant's liver stops producing AFP; an adult liver contains only trace amounts. During pregnancy, the fetus excretes AFP in urine, and some of the protein crosses the fetal membranes to enter the mother's blood. The level of AFP can then be determined by analyzing a sample of the mother's blood.
By analyzing the amount of AFP found in a blood or amniotic fluid sample, doctors can determine the probability that the fetus is at risk for certain birth defects. It is very important that the doctor know precisely how old the fetus is when the test is performed, because the AFP level changes over the length of the pregnancy. AFP screening is used as an indicator of risk and then an appropriate line of testing (like amniocentesis or ultrasound) follows, based on the results.
Abnormally high AFP may indicate that the fetus has an increased risk of a neural tube defect, the most common and severe type of disorder associated with increased AFP. These types of defects include spinal column defects (spina bifida) and anencephaly (a severe and usually fatal brain abnormality).
If the tube that becomes the brain and spinal cord does not close correctly during fetal development, AFP may leak through this abnormal opening and enter the amniotic fluid. This leakage creates abnormally high levels of AFP in amniotic fluid and in maternal blood.
Created on Dec 31st 1969 19:00. Viewed 0 times.
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