title: The NTplus method of screening for Down syndrome: achieving the 2010 targets?
abstract: BACKGROUND
  The performance of pregnancy-associated plasma protein-A (PAPP-A) as a first trimester trisomy 21 marker is hypothesized to improve below 11 weeks, whereas beta-human chorionic gonadotrophin (hCG) is better after 14 weeks. We audited a model combining early PAPP-A (9-10 weeks) with NT (11-13 weeks and 6 days) and early triple test (>14 weeks).
  
  
  METHODS
  A total of 1507 women with viable ongoing pregnancies were screened during 2007-2008. First-stage 'screen-positive' risk was based on combined PAPP-A and NT cut-off >or=1 : 100. Where first-stage risk was <1 : 100 or invasive testing declined, triple test was performed and a combined second-stage risk given with cut-off >or=1 : 250 being screen positive.
  
  
  RESULTS
  Median age of women was 35.4 years. Sixty-four (4.2%) were 'screen positive'. Of these, 11 had a fetus with trisomy 21. Twelve pregnancies were affected with trisomy 21, giving a detection rate of 11/12 (92%) with a false-positive rate (FPR) of 3.2%. The screen-positive rate (SPR) and FPR were 1.93 and 1.44%, respectively, standardized to median maternal age 29.
  
  
  CONCLUSIONS
  Early PAPP-A, NT and later triple testing offers comparable detection for trisomy 21 to published data for first trimester combined testing but feasibly achieve the national target for 2010 of 90% detection of trisomy 21 for < 2% SPR.
authors.affiliation: Department of Fetal Medicine, Cambridge University Hospitals NHS Trust, Cambridge, United Kingdom.
authors.forename: Osama
authors.initials: O
authors.lastname: Habayeb
authors.forename: Sandy
authors.initials: S
authors.lastname: Goodburn
authors.forename: Trish
authors.initials: T
authors.lastname: Chudleigh
authors.forename: Jeremy
authors.initials: J
authors.lastname: Brockelsby
authors.forename: Hannah
authors.initials: H
authors.lastname: Missfelder-Lobos
authors.forename: Gerald
authors.initials: G
authors.lastname: Hackett
authors.forename: Christoph
authors.initials: C
authors.lastname: Lees
mesh_terms: D000293:Adolescent; D000328:Adult; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood*; D004314:Down Syndrome / Q000097:blood* / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008875:Middle Aged; D048208:Nuchal Translucency Measurement; D011237:Predictive Value of Tests; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011266:Pregnancy-Associated Plasma Protein-A / Q000032:analysis*; D055815:Young Adult
chemical_list: D018997:Chorionic Gonadotropin, beta Subunit, Human; D011266:Pregnancy-Associated Plasma Protein-A