title: First trimester contingent screening for trisomies 21,18,13: is this model cost efficient and feasible in public health system?
abstract: OBJECTIVE
  To evaluate the effectiveness of three different first trimester screening models for trisomies 21, 18 and 13, in terms of detection rate, invasive test rate and final costs.
  
  
  METHODS
  We analyzed the distribution of risk for trisomies 21, 18 and 13 in a population of 20,831 singleton pregnancies based on maternal age, fetal heart rate, nuchal translucency, free beta human chorionic gonadotropin and pregnancy-associated plasma protein A (Combined test). On the basis of our data, we estimated the performance and cost of screening for trisomies using three different models at specific cutoffs: Combined test; Cell free DNA test and Contingent screening test.
  
  
  RESULTS
  Using Combined test, DR for major trisomies was estimated to be 94.92%, invasive test rate was 6.3%. cfDNA would result in a DR of 97.92%, with an invasive test rate of 3.64%. Contingent screening approach would result in an overall DR of 97.82, with a rate for invasive procedure of 1.36% and a final cost lower than other screening policies (2,338,433 euro vs 5,796,060 of cfDNA and 2,385,473 of Combined test).
  
  
  CONCLUSIONS
  Contingent screening test could be a cost-efficient and feasible first trimester screening test for aneuploidies in public health system.
authors.affiliation: a Center for Reproductive Medicine and BirthCare Program, Hospital Misericordia, Azienda USL Toscana Sud Est , Grosseto , Italy.
authors.forename: Enrico
authors.initials: E
authors.lastname: Colosi
authors.affiliation: b Department of Experimental Medicine , University of Rome "Sapienza", Umberto I Hospital , Rome , Italy.
authors.forename: Valentina
authors.identifier: http://orcid/org/0000-0002-3820-1030
authors.initials: V
authors.lastname: D'Ambrosio
authors.affiliation: c Prenatal Diagnosis Unit , Palagi Hospital , Florence , Italy.
authors.forename: Enrico
authors.initials: E
authors.lastname: Periti
mesh_terms: D000328:Adult; D002882:Chromosomes, Human, Pair 13; D002887:Chromosomes, Human, Pair 18; D003362:Cost-Benefit Analysis; D004314:Down Syndrome / Q000175:diagnosis; D005260:Female; D006801:Humans; D008423:Maternal Age; D062145:Maternal Serum Screening Tests / Q000191:economics; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011296:Prenatal Diagnosis / Q000191:economics* / Q000379:methods; D011634:Public Health / Q000191:economics*; D014314:Trisomy / Q000175:diagnosis*
keywords: Prenatal screening; cell-free DNA; contingent screening test; first trimester; nuchal translucency