title: IONA test for first-trimester detection of trisomies 21, 18 and 13.
abstract: OBJECTIVE
  To assess the potential performance of screening for fetal trisomies 21, 18 and 13 by cell-free DNA (cfDNA) analysis of maternal blood using the IONA® test.
  
  
  METHODS
  This was a nested case-control study of cfDNA analysis of maternal plasma using the IONA test. Samples were obtained at 11-13 weeks' gestation, before chorionic villus sampling, from 201 euploid pregnancies, 35 with trisomy 21, four with trisomy 18 and two with trisomy 13. Laboratory personnel were blinded to the fetal karyotype.
  
  
  RESULTS
  Probability scores for trisomies 21, 18 and 13 were given for 241/242 samples analyzed. No probability score was provided for one (0.5%) euploid pregnancy because of low fetal fraction. In all 35 cases of trisomy 21 the probability score for trisomy 21 was > 95% and the scores for trisomies 18 and 13 were ≤ 0.0001%. In all four cases of trisomy 18, the probability score for trisomy 18 was > 77% and the scores for trisomies 21 and 13 were ≤ 0.0001%. In the two cases of trisomy 13, the probability score for trisomy 13 was > 59% and the scores for trisomies 21 and 18 were ≤ 0.0001%. In the 200 euploid pregnancies with a test result, the probability score was < 0.08% for trisomy 21, < 0.001% for trisomy 18 and < 0.002% for trisomy 13. Therefore, the IONA test detected 100% of all three trisomies, with a false-positive rate of 0%.
  
  
  CONCLUSIONS
  The IONA test successfully differentiated all cases of trisomies 21, 18 and 13 from euploid pregnancies.
authors.affiliation: Harris Birthright Research Centre for Fetal Medicine, King's College Hospital, London, UK.
authors.forename: L C
authors.initials: LC
authors.lastname: Poon
authors.affiliation: Harris Birthright Research Centre for Fetal Medicine, King's College Hospital, London, UK.
authors.forename: D
authors.initials: D
authors.lastname: Dumidrascu-Diris
authors.affiliation: Harris Birthright Research Centre for Fetal Medicine, King's College Hospital, London, UK.
authors.forename: C
authors.initials: C
authors.lastname: Francisco
authors.affiliation: Harris Birthright Research Centre for Fetal Medicine, King's College Hospital, London, UK.
authors.forename: I
authors.initials: I
authors.lastname: Fantasia
authors.affiliation: Harris Birthright Research Centre for Fetal Medicine, King's College Hospital, London, UK.
authors.forename: K H
authors.initials: KH
authors.lastname: Nicolaides
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D025063:Chromosome Disorders / Q000175:diagnosis* / Q000196:embryology / Q000235:genetics; D002882:Chromosomes, Human, Pair 13 / Q000235:genetics; D002887:Chromosomes, Human, Pair 18 / Q000235:genetics; D004314:Down Syndrome / Q000175:diagnosis* / Q000196:embryology / Q000235:genetics; D005260:Female; D005820:Genetic Testing / Q000379:methods*; D005865:Gestational Age; D006801:Humans; D008423:Maternal Age; D062145:Maternal Serum Screening Tests / Q000379:methods*; D011237:Predictive Value of Tests; D011247:Pregnancy; D011261:Pregnancy Trimester, First / Q000097:blood*; D014314:Trisomy / Q000175:diagnosis* / Q000235:genetics; D000073839:Trisomy 13 Syndrome; D000073842:Trisomy 18 Syndrome
keywords: aneuploidy; cell-free DNA; first trimester; first-trimester screening; prenatal diagnosis