What Is The Quad Screen?
The Quad Test is a second trimester screening (15 weeks to 22 weeks and 6 days) that assesses the risk of a baby being born with Down syndrome, Trisomy 18, or open neural tube defects (ONTDs).
In this test, the levels of four substances in the serum that are markers of Down syndrome are examined:
- Alpha-fetoprotein (AFP)
- Total beta-human chorionic gonadotropin (total ß-hCG)
- Unconjugated Estriol (uE3)
In a Down syndrome affected pregnancy, the levels of AFP and estriol tend to be lower than normal while the levels of total ß–hCG and inhibin A are elevated. In a pregnancy affected by ONTDs, the level of AFP tends to be elevated. In a Trisomy 18 affected pregnancy, levels of AFP, estriol, and ß–hCG tend to be reduced.
What Does a Screen Positive Result for Down Syndrome Mean?
- A screen positive for the AFP+Quad Test means that you have a risk of greater than or equal to 1 in 270 of having a Down syndrome pregnancy. About 1 in 20 women (5%) who take this test receive a screen positive result.
What Are The Tests That Will Be Offered If An AFP+Quad Test Is Screen Positive?
- Depending on the results of the AFP+Quad Test and the sonogram, further diagnostic testing such as amniocentesis or more detailed ultrasound studies may be recommended.