title: Positive predictive values for detection of trisomies 21, 18 and 13 and termination of pregnancy rates after referral for advanced maternal age, first trimester combined test or ultrasound abnormalities in a national screening programme (2007-2009).
abstract: OBJECTIVE
  The objective of this article is to analyse the positive predictive value (PPV) of trisomies 21, 18 and 13 after referral for advanced maternal age (AMA), first trimester combined test or ultrasound findings to suggest improvements for clinical practice.
  
  
  METHODS
  Data (48 457 combined tests, 134 000 fetal anomaly scans and 24 379 invasive prenatal tests) were combined to calculate PPV and termination of pregnancy rates.
  
  
  RESULTS
  For referral for AMA, the PPV for T21 was 1.0% and 1.8% for amniocentesis and chorionic villus biopsy, respectively; for the combined test at a maternal age ≥36 years, these percentages were 4.9% and 12.5%, respectively and for maternal age <36 years, 4.4% and 8.1%, respectively. For ultrasound findings, the PPV was 5.3% and 14.8%, respectively. Termination of pregnancy rate upon trisomy 21 diagnosis was >90% unless detected after referral for ultrasound findings (71.5-85.9%). About 50% of pregnant women with a high combined test risk chose not to have invasive testing.
  
  
  CONCLUSIONS
  Advanced MA is still a large contributor to invasive testing but should be abandoned (low PPV, high fetal loss rate) and be replaced by reimbursable combined test screening for all women. Patient information on second trimester ultrasound screening should indicate that abnormal ultrasound findings are associated with high trisomy rate.
authors.affiliation: Reference Laboratory for Pre- and Neonatal Screening/Laboratory for Infectious Diseases and Screening, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.
authors.forename: Jacqueline E
authors.initials: JE
authors.lastname: Siljee
authors.forename: Alida C
authors.initials: AC
authors.lastname: Knegt
authors.forename: Maarten F C M
authors.initials: MF
authors.lastname: Knapen
authors.forename: Mireille N
authors.initials: MN
authors.lastname: Bekker
authors.forename: Gerard H A
authors.initials: GH
authors.lastname: Visser
authors.forename: Peter C J I
authors.initials: PC
authors.lastname: Schielen
mesh_terms: D000028:Abortion, Induced / Q000706:statistics & numerical data*; D000328:Adult; D005260:Female; D006801:Humans; D008403:Mass Screening; D008423:Maternal Age; D009426:Netherlands; D011237:Predictive Value of Tests; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D012189:Retrospective Studies; D014314:Trisomy / Q000175:diagnosis*; D016216:Ultrasonography, Prenatal