Detection of aneuploidy in 1st trimester:

Ans. A. hCG and PAPP-ARef: William's 24th/ed, p289Table 2: Selected Down syndrome screening strategies and their detection rateStrategyAnalytesDetection Rate3 (%)First-trimester screenNT, PAPP-A, and hCG or free p-hCG79-87NTNT alone64-70Triple testMSAFP hCG OR free p-hCG, uE361-70Quadruple (Quad) testMSAFP, hCG or free p-hCG, uE3, inh74-81Integrated screenFirst-trimester screen and Quad test; results withheld until Quad test completed94-96Stepwise sequentialFirst-trimester screen and Quad test 1% offered diagnostic test after first-trimester screen 99% proceed to Quad test, results withheld until Quad test completed90-95Contingent sequential screenFirst-trimester screen and Quad test 1 % offered diagnostic test after first-trimester screen 15% proceed to Quad test; results withheld until Quad test completed84% have no additional test after first trimester screen88-94Cell-free fetal DNA testing (high-risk pregnancies)No analytes--massively parallel genomic sequencing98aBased on a 5% positive screen rate.Free b-hCG = free b-subunit hCG; hCG = human chorionic gonadotropin, inh = dimeric inhibin a;MSAFP = maternal serum alpha-fetoprotein; NT = nuchal translucency; PAPP-A = pregnancy-associated plasma protein-A; uE3 = unconjugated estriol.