AFP (Alpha-Fetoprotein); AFP-AF (Alpha-Fetoprotein, Amniotic Fluid); Alpha Fetoprotein, Amniotic Fluid; Alpha-Fetoprotein, Amniotic Fluid; Fetoprotein, Amniotic Fluid
If alpha-fetoprotein is positive, then acetylcholinesterase will be performed at an additional charge.
Do not centrifuge.
1. The following information is required:
All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.
This test is for screening only.
Increases in alpha-fetoprotein (AFP) are not specific for neural tube defects, and the test must be used in combination with other procedures such as ultrasonography and acetylcholinesterase measurements.
Elevated AFP levels also can be caused by benign factors and incorrect gestational dating.
Negative results do not guarantee the absence of defects.
Alpha-fetoprotein (AFP) is a single polypeptide chain glycoprotein with a molecular weight of approximately 70,000 Da. Synthesis of AFP occurs primarily in the liver and yolk sac of the fetus. It is secreted in fetal serum, reaching a peak at approximately 13 weeks gestation, after which it rapidly declines until about 22 weeks gestation and then gradually declines until term. Transfer of AFP into maternal circulation is accomplished primarily through diffusion across the placenta. Maternal serum AFP levels rise from the normal non-pregnancy level of 0.20 ng/mL to about 250 ng/mL at 32 weeks gestation.
If the fetus has an open neural tube defect, AFP is thought to leak directly into the amniotic fluid causing unexpectedly high concentrations of AFP. Other fetal abnormalities such as omphalocele, gastroschisis, congenital renal disease, and esophageal atresia; and other fetal distress situations such as threatened abortion, prematurity, and fetal demise, may also show AFP elevations. Decreased amniotic fluid AFP values may be seen when gestational age has been overestimated.