Quad screen is also known as the quadruple marker test or simply the quad test . It is a maternal blood screening test that measures the level of 4 specific substances. They are
- Alpha-fetoprotein (AFP) which is a protein made by the fetus
- Human chorionic gonadotropin (HCG), which is a hormone produced by the placenta
- Estriol is estrogen produced by both the fetus and placenta
- Inhibin A is a protein produced by the placenta and ovaries
The quad screen is almost the same as the triple screen test. However, the quad screen not only looks for the three specific substances evaluated in those tests (AFP, hCG, and Estriol) but also a fourth substance known as Inhibin-A.
To determine your chances of having a child with birth defects, the test takes into consideration the following :
- ethnic background
- baby’s gestational age
How is the quad screen performed ?
During this test, the maternal blood is drawn. This may take about 5 to 10 minutes. The blood is then taken to the lab for testing. Results are usually back in a few days.
Who needs a quad screen ?
This test should be offered to all pregnant women however it is recommended for women who fall into the following category.
- age 35 and above
- have a family history of birth defects
- have diabetes and use insulin
- have a viral infection during pregnancy
- women who have used harmful medications during pregnancy
- have been exposed to high level of radiation
Why is a quad screen done ?
It is done to evaluate your risk of having a baby with the following conditions
- down syndrome -trisomy 21
- spina bifida
- Edwards syndrome – trisomy 18
What does a quad screen look out for ?
The quad screen measures the following :
- high and low levels of AFP
- abnormal levels of hCG
- abnormal levels of estriol
- high levels of Inhibin-A
The results are combined with factors such as the mother’s age and ethnicity to assess the possibility of having a child with genetic abnormalities.
High levels of AFP may indicate that developing baby has a neural tube defect such as spina bifida, anencephaly, Turner’s syndrome and other genetic problems. However high levels of AFP are usually caused by inaccurate dating of the pregnancy or that you are carrying multiple babies.
Low levels of AFP and abnormal levels of hCG and estriol may suggest the baby has Down syndrome , Edwards syndrome or other chromosomal abnormalities.
What do the results mean ?
The result of a quad screen only suggest that the mother is at risk of carrying a baby with genetic disorders. It doesn’t mean the baby has genetic disorders. Most women who get abnormal results deliver healthy babies.
If you result come back abnormal, you may have further testing such as a high definition ultrasound or amniocentesis to make a diagnosis.
Further testing to make a diagnosis may help you plan emotionally and physically for a child with special needs. However, this is totally optional. Some people may opt not to undergo further testing due to personal, moral, or religious reasons. It is important to discuss the benefits and risk of this test with your doctor.
Quad screen . Mayo Foundation. http://www.mayoclinic.org/tests-procedures/quad-screen/basics/definition/prc-20013408. Accessed January 2, 2015
Quadruple screen test. National Library of Medicine. MedlinePlus. http://www.nlm.nih.gov/medlineplus/ency/article/007311.htm. Accessed January 2, 2015