title: Advantages and Disadvantages of Different Implementation Strategies of Non-Invasive Prenatal Testing in Down Syndrome Screening Programmes.
abstract: BACKGROUND
  Implementation of non-invasive prenatal testing (NIPT) in Down syndrome screening programmes requires health policy decisions about its combination with other tests and its timing in pregnancy.
  
  
  OBJECTIVE
  Our aim was to aid health policy decision makers by conducting a quantitative analysis of different NIPT implementation strategies.
  
  
  METHODS
  Decision trees were created to illustrate all plausible alternatives in a theoretical cohort of 100,000 pregnant women in five screening programmes: classical screening by the first-trimester combined test (FCT), pre-selection of high-risk women prior to NIPT by the FCT, NIPT as the first screening test at 10 weeks and at 13 weeks, and the simultaneous conductance of NIPT and the FCT.
  
  
  RESULTS
  Pre-selection by FCT prior to NIPT reduces the number of amniocenteses to a minimum because of a reduction of false-positive NIPT results. If NIPT is the first screening test, it detects almost all fetal Down syndrome cases. NIPT at 10 weeks reassures women early in pregnancy, while NIPT at 13 weeks prevents unnecessary tests due to spontaneous miscarriages and allows for immediate confirmation by amniocentesis.
  
  
  CONCLUSIONS
  Every implementation strategy has its advantages and disadvantages. The most favourable implementation strategy may be NIPT as the first screening test at 13 weeks, offering the most accurate screening test for Down syndrome, when the risk for spontaneous miscarriage has declined remarkably and timely confirmation by amniocentesis can be performed.
authors.affiliation: Department of Clinical Genetics, Maastricht University Medical Centre+, Maastricht, The Netherlands.
authors.forename: Elke
authors.initials: E
authors.lastname: Mersy
authors.forename: Christine E M
authors.initials: CE
authors.lastname: de Die-Smulders
authors.forename: Audrey B C
authors.initials: AB
authors.lastname: Coumans
authors.forename: Luc J M
authors.initials: LJ
authors.lastname: Smits
authors.forename: Guido M W R
authors.initials: GM
authors.lastname: de Wert
authors.forename: Suzanna G M
authors.initials: SG
authors.lastname: Frints
authors.forename: Joris A
authors.initials: JA
authors.lastname: Veltman
mesh_terms: D000022:Abortion, Spontaneous / Q000209:etiology / Q000517:prevention & control; D000649:Amniocentesis / Q000379:methods / Q000706:statistics & numerical data; D003663:Decision Trees; D004314:Down Syndrome / Q000175:diagnosis*; D042241:Early Diagnosis; D005260:Female; D006291:Health Policy; D006801:Humans; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011296:Prenatal Diagnosis / Q000379:methods*; D012307:Risk Factors; D012680:Sensitivity and Specificity; D019564:Unnecessary Procedures / Q000706:statistics & numerical data