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Elevated alpha-fetoprotein refers to a state where alpha-fetoprotein levels are outside of the reference range. There are two categories of AFP tests: tests performed on serum (blood plasma), and tests performed on amniotic fluid. Tests performed on serum are further categorized by the reason for performing the test: maternal serum, adult tumor ...
Fetal abnormalities are conditions that affect a fetus or embryo, are able to be diagnosed prenatally, and may be fatal or cause disease after birth.They may include aneuploidies, structural abnormalities, or neoplasms.
Alpha-fetoprotein (AFP, α-fetoprotein; also sometimes called alpha-1-fetoprotein, alpha-fetoglobulin, or alpha fetal protein) is a protein [5] [6] that in humans is encoded by the AFP gene. [ 7 ] [ 8 ] The AFP gene is located on the q arm of chromosome 4 (4q13.3). [ 9 ]
It is a tetramer protein with 2 alpha and 2 gamma subunits. This is different from adult hemoglobin because it has 2 alpha and 2 beta subunits. Fetal hemoglobin is coded by a gene on chromosome 11. The gamma subunit on fetal hemoglobin contains a neutral and nonpolar amino acid at position 136, unlike the beta subunit of adult hemoglobin.
The most common abnormality the test can screen is trisomy 21 (Down syndrome).In addition to Down syndrome, the triple and quadruple screens assess risk for fetal trisomy 18 also known as Edwards syndrome, open neural tube defects, and may also detect an increased risk of Turner syndrome, triploidy, trisomy 16 mosaicism, fetal death, Smith–Lemli–Opitz syndrome, and steroid sulfatase ...
The second trimester screen looks at specific blood markers, to include the estriol, inhibin and human chorionic gonadotropin hormones and often consists of Alpha-fetoprotein (AFP) screening. Any abnormal results from these screening tests can indicate the possibility of abnormal conditions such as Trisomy 18, Trisomy 21 (Down syndrome), and ...
As an example, Alpha-fetoprotein (AFP) testing is used to screen for a neural tube defect (NTD) during the second trimester of pregnancy. If the median AFP result at 16 weeks of gestation is 30 ng/mL and a pregnant woman's AFP result at that same gestational age is 60 ng/mL, then her MoM is equal to 60/30 = 2.0.
Before birth, if a blood test or amniocentesis finds a high level of alpha-fetoprotein (AFP), there is a higher risk of spina bifida. [5] Ultrasound examination may also detect the problem. Medical imaging can confirm the diagnosis after birth. [ 5 ]