What does the Quad screen primarily screen for?

The Quad screen is a specific prenatal test that primarily screens for the risk of certain chromosomal abnormalities, notably Trisomy 21 (Down syndrome) and Trisomy 18 (Edward syndrome). This screening test combines four key biomarkers found in a pregnant woman's blood: alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG), unconjugated estriol (uE3), and inhibin A (Inhibin-A). Each of these biomarkers has predictive value for assessing the likelihood of these chromosomal conditions.

Trisomy 21 is associated with elevated levels of hCG and inhibin A, as well as reduced levels of AFP and uE3. In contrast, Trisomy 18 typically presents with lower levels of all four markers. By analyzing these biomarkers, the Quad screen can provide valuable information and risk assessment regarding the presence of these genetic conditions.

Other options present relevant screening parameters but do not fully capture the primary focus of the Quad screen. For instance, neural tube defects and spinal bifida are generally screened using different tests, such as the serum-alpha fetoprotein (AFP) test, rather than the Quad screen specifically.