title: Impact of Including or Removing Nuchal Translucency Measurement on the Detection and False-Positive Rates of First-Trimester Down Syndrome Screening.
abstract: BACKGROUND
  First-trimester Down syndrome (DS) screening combining maternal age, serum markers (pregnancy-associated plasma protein-A and beta-human chorionic gonadotropin) and nuchal translucency (NT) gives an 85% detection rate for a 5% false-positive rate. These results largely depend on quality assessment of biochemical markers and of NT. In routine practice, despite an ultrasound quality control organization, NT images can be considered inadequate. The aim of the study was to evaluate the consequences for risk calculation when NT measurement is not taken into account.
  
  
  METHODS
  Comparison of detection and false-positive rates of first-trimester DS screening (PerkinElmer, Turku, Finland), with and without NT, based on a retrospective study of 117,126 patients including 274 trisomy 21-affected fetuses. NT was measured by more than 3,000 certified sonographers.
  
  
  RESULTS
  There was no significant difference in detection rates between the two strategies including or excluding NT measurement (86.7 vs. 81.8%). However, there was a significant difference in the false-positive rates (2.23 vs. 9.97%, p < 0.001).
  
  
  CONCLUSIONS
  Sonographers should be aware that removing NT from combined first-trimester screening would result in a 5-fold increase in false-positive rate to maintain the expected detection rates. This should be an incentive for maintaining quality in NT measurement.
authors.affiliation: Department of Obstetrics and Maternal Fetal Medicine, Necker-Enfants Malades Hospital, AP-HP, Paris, France.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Spaggiari
authors.forename: Isabelle
authors.initials: I
authors.lastname: Czerkiewicz
authors.forename: Corinne
authors.initials: C
authors.lastname: Sault
authors.forename: Sophie
authors.initials: S
authors.lastname: Dreux
authors.forename: Armelle
authors.initials: A
authors.lastname: Galland
authors.forename: Laurent J
authors.initials: LJ
authors.lastname: Salomon
authors.forename: Yves
authors.initials: Y
authors.lastname: Ville
authors.forename: Françoise
authors.initials: F
authors.lastname: Muller
mesh_terms: D000328:Adult; D004314:Down Syndrome / Q000000981:diagnostic imaging*; D005189:False Positive Reactions; D005260:Female; D005865:Gestational Age; D006801:Humans; D008423:Maternal Age; D048208:Nuchal Translucency Measurement / Q000592:standards*; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D012189:Retrospective Studies