A prenatal screening test for Down syndrome, so named because it is a triple test—which measures beta-hCG, alpha fetoprotein and oestriol—plus inhibin. Blood is drawn for the test at 16 to 18 weeks of gestation.
Results Elevated inhibin A and beta-hCG, and reduced AFP and oestriol are strongly suggestive of a Down syndrome baby. These results give the mother the option to abort the gestation in the early second trimester.
Synonyms Quad screen, quadruple screen, quadruple test, tetra screen, tetra test