Would you like to know what lab results mean? Medical Tests Analyzer Software will explain and clarify your lab test report.

The triple or quad screen is used as a screening test in the second trimester of pregnancy. It is ordered to help evaluate the risk that a fetus has certain abnormalities, including Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), and neural tube defects such as spina bifida or a condition called anencephaly.
These tests have been established as a triple or quad screen because their power lies in their use together. A mathematical calculation involving the levels of these 3 or 4 substances (AFP, hCG, unconjugated estriol (uE3), and, sometimes, inhibin A(DIA)) and considerations of maternal age, family history, weight, race, and diabetic status are used to determine a numeric risk for Down syndrome and for a few other chromosomal abnormalities such as Edwards syndrome (trisomy 18) in the fetus. This risk is compared with an established cut-off. If the risk is higher than the cut-off value, then it is considered a positive screening test or increased risk exists for carrying a fetus with one of the discussed abnormalities.
An AFP test may be performed by itself and not as part of a triple or quad screen, especially when First Trimester Screening has already been used to assess the risk for chromosomal abnormalities. The AFP is used to help determine the risk of neural tube defects.
The test is usually ordered between the 15th and 21st weeks of pregnancy.

Test results
The interpretation of a test result should be provided by a genetic counselor or clinician who can explain the meaning of the results and offer choices about follow-up. It is important to remember that screening tests are not diagnostic of a fetal abnormality; they indicate a normal or increased risk. Of all women who have positive triple or quad screening results, only a very small number of them have babies who actually have a neural tube defect or chromosomal abnormality.
In pregnancies where the fetus is carrying the chromosomal defect that results in Down syndrome (trisomy 21), the levels of AFP and unconjugated estriol tend to be low and hCG and inhibin A levels high.
In pregnancies where the fetus has Edwards syndrome (trisomy 18), unconjugated estriol and hCG levels are low and AFP levels can be variable.
A baby with an open neural tube defect has an opening in its spine, head, or abdominal wall that allows higher-than-usual amounts of AFP to pass into the mother's blood. The other markers are not used in the evaluation of risk for carrying a fetus with a neural tube defect.
If a screen is positive, tests that are more definitive are needed to determine and confirm a diagnosis. These include high-resolution ultrasound and perhaps amniocentesis followed by chromosome analysis. These follow-up tests are used to help women and their doctors make decisions about the management of their pregnancies.
The triple screen can detect about 70% of fetuses affected by Down syndrome while the quad screen can detect about 80%. Either screen can detect about 75-80% of those affected with spina bifida and 95% cases of anencephaly.
Not all fetal abnormalities will give positive test results.

Risk Cutoff
Neural Tube Defect
>2.0 MOM
Down Syn
Trisomy 18

Neural Tube Defect Screening: Elevated Maternal serum AFP levels indicate an increased risk for open spina bifida and anencephaly. Other risk factors include family history of neural tube defects, certain maternal drug exposures, and maternal insulin-dependent diabetes. More definitive tests such as high-resolution ultrasound, amniotic fluid AFP, and acetycholinesterase are recommended when there is an increase risk for an open neural tube defect. Adverse pregnancy outcomes associated with elevated maternal serum AFP are prematurity, growth retardation, low birth weight, and fetal demise.
Down Syndrome Screening: Maternal serum screening for Down syndrome utilizes the maternal age specific risk and second trimester levels of AFP, hCG, uE3, and DIA to calculate a risk estimate for each pregnancy. A positive screen for Down syndrome is reported when the risk is greater than or equal to 1:270. Risks less than 1:270 are reported as a negative screen.
Trisomy 18 Screening: The estimated trisomy 18 risk for each pregnancy is calculated based on the maternal age risk and the levels of AFP, hCG, and uE3. A positive screen for trisomy 18 is reported when the risk is greater than or equal to 1:100.

Also you should know
The test result is very dependent on accurate determination of the gestational age of the fetus. If the gestational age of the fetus has not been accurately determined, the results may be either falsely high or low.
In multiple gestation pregnancies, calculation of the risk of Down syndrome or Edwards syndrome is difficult. For twin pregnancies, a "pseudorisk" can be calculated comparing results to normal results in other twin pregnancies. For higher gestation pregnancies, risk cannot be calculated from these tests.
Evaluation of the risk of open neural tube defects in twin pregnancies can be determined, although it is not as effective as in singleton pregnancies.
If you have had a First Trimester Screen, then a triple/quad screen (second trimester screening) is not performed because the risks for Down syndrome and Edwards syndrome have already been assessed. However, if you and your doctor wish to use the results of both first and second trimester screening to assess the risk of chromosome abnormalities, then integrated or sequential screening may be employed. For more on these, see the article on First Trimester Screening.

Things that may affect the results of your test include:  
·If there is more than one baby (fetus). This increases the level of AFP in the blood.  
·If you have gestational diabetes.  
·If you smoke. This increases the level of AFP in the blood.  
·If you had a medical test that used radioactive tracers in the past 2 weeks.  

Down syndrome (DS) is a chromosomal abnormality, also called trisomy 21, that affects about 1 in 800 live births. People with DS have an extra copy of part or all of chromosome 21. Most affected children have some retardation of growth and development. The risk of carrying a fetus with Down syndrome increases with the mother's age, especially in women over 40 years old. For more information, visit the National Down Syndrome Society.

Neural tube defects are serious birth defects: the brain, spinal cord, or their coverings do not develop completely. There are three kinds of neural tube defects:
·Anencephaly: incomplete development of the brain and the skull  
·Encephalocele: a hole in the skull through which brain tissue protrudes  
·Spina bifida: the most common neural tube defect, in which the spine does not close properly during early pregnancy (For more information on spina bifida, visit the Spina Bifida Association of America.)  
To help prevent formation of a neural tube defect the U.S. Public Health Service recommends that all women of childbearing age should take 0.4 mg of folic acid daily.

Edwards syndrome (trisomy 18) is a condition in which there are 3 copies of chromosome 18. The risk of carrying a fetus with Edwards syndrome also increases with maternal age. Edwards syndrome is associated with multiple abnormalities and is usually fatal, with live-born infants rarely living beyond one year of age. The frequency of this abnormality is much less than Down syndrome, occurring in only 1 in 3000 live births. For more information, see the Trisomy 18 Foundation web site.

All information on this page is intended for your general knowledge only and does not provide medical advice, diagnosis or treatment.