title: First-trimester screening for trisomies 21, 18 and 13 by ultrasound and biochemical testing.
abstract: OBJECTIVE
  To examine the performance of screening for trisomies 21, 18 and 13 at 11-13 weeks' gestation using specific algorithms for these trisomies based on combinations of fetal nuchal translucency thickness (NT), fetal heart rate (FHR), ductus venosus pulsatility index for veins (DV PIV), and serum free β-human chorionic gonadotropin (β-hCG), pregnancy-associated plasma protein A (PAPP-A), placental growth factor (PLGF) and α-fetoprotein (AFP).
  
  
  METHODS
  Model-based estimates of screening performance were produced for the distribution of maternal ages in England and Wales in 2011, and prospectively collected data on fetal NT, FHR, DV PIV, β-hCG, PAPP-A, PLGF and AFP from singleton pregnancies undergoing aneuploidy screening.
  
  
  RESULTS
  In screening by NT, FHR, free β-hCG and PAPP-A, using specific algorithms for trisomy 21 and trisomies 18 and 13 at the risk cutoff of 1:100, the estimated detection rate (DR) was 87.0% for trisomy 21 and 91.8% for trisomies 18 and 13, at a false-positive rate (FPR) of 2.2%. Addition of PLGF, AFP and DV PIV increased the DR to 93.3% for trisomy 21 and 95.4% for trisomies 18 and 13 and reduced the FPR to 1.3%.
  
  
  CONCLUSIONS
  Effective screening for trisomies can be achieved using specific algorithms based on NT, FHR, DV PIV, β-hCG, PAPP-A, PLGF and AFP.
authors.affiliation: Centre for Medical Statistics and Bioinformatics, University of Exeter, Exeter, UK.
authors.forename: D
authors.initials: D
authors.lastname: Wright
authors.forename: A
authors.initials: A
authors.lastname: Syngelaki
authors.forename: I
authors.initials: I
authors.lastname: Bradbury
authors.forename: R
authors.initials: R
authors.lastname: Akolekar
authors.forename: K H
authors.initials: KH
authors.lastname: Nicolaides
mesh_terms: D000465:Algorithms; D006063:Chorionic Gonadotropin / Q000097:blood; D025063:Chromosome Disorders / Q000175:diagnosis*; D002882:Chromosomes, Human, Pair 13 / Q000648:ultrastructure; D002887:Chromosomes, Human, Pair 18 / Q000000981:diagnostic imaging; D004314:Down Syndrome / Q000175:diagnosis* / Q000000981:diagnostic imaging; D005260:Female; D006340:Heart Rate, Fetal; D006801:Humans; D008423:Maternal Age; D048208:Nuchal Translucency Measurement; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011266:Pregnancy-Associated Plasma Protein-A / Q000378:metabolism; D014314:Trisomy / Q000175:diagnosis*; D000073839:Trisomy 13 Syndrome; D000073842:Trisomy 18 Syndrome
chemical_list: D006063:Chorionic Gonadotropin; D011266:Pregnancy-Associated Plasma Protein-A