title: Noninvasive prenatal testing in routine clinical practice--an audit of NIPT and combined first-trimester screening in an unselected Australian population.
abstract: BACKGROUND
  There are limited data regarding noninvasive prenatal testing (NIPT) in low-risk populations, and the ideal aneuploidy screening model for a pregnant population has yet to be established.
  
  
  OBJECTIVE
  To assess the implementation of NIPT into clinical practice utilising both first- and second-line screening models.
  
  
  METHODS
  Three private practices specialising in obstetric ultrasound and prenatal diagnosis in Australia offered NIPT as a first-line test, ideally followed by combined first-trimester screening (cFTS), or as a second-line test following cFTS, particularly in those with a calculated risk between 1:50 and 1:1000.
  
  
  RESULTS
  NIPT screening was performed in 5267 women and as a first-line screening method in 3359 (63.8%). Trisomies 21 and 13 detection was 100% and 88% for trisomy 18. Of cases with known karyotypes, the positive predictive value (PPV) of the test was highest for trisomy 21 (97.7%) and lowest for monosomy X (25%). Ultrasound detection of fetal structural abnormality resulted in the detection of five additional chromosome abnormalities, two of which had high-risk cFTS results. For all chromosomal abnormalities, NIPT alone detected 93.4%, a contingent model detected 81.8% (P = 0.097), and cFTS alone detected 65.9% (P < 0.005).
  
  
  CONCLUSIONS
  NIPT achieved 100% T21 detection and had a higher DR of all aneuploidy when used as a first-line test. Given the false-positive rate for all aneuploidies, NIPT is an advanced screening test, rather than a diagnostic test. The benefit of additional cFTS was the detection of fetal structural abnormalities and some unusual chromosomal abnormalities.
authors.affiliation: Sydney Ultrasound for Women, Sydney, New South Wales, Australia.|Sydney University, Sydney, New South Wales, Australia.
authors.forename: Andrew
authors.initials: A
authors.lastname: McLennan
authors.affiliation: Women's Ultrasound, Melbourne, Victoria, Australia.|University of Melbourne, Melbourne, Victoria, Australia.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Palma-Dias
authors.affiliation: University of Melbourne, Melbourne, Victoria, Australia.|Monash Ultrasound for Women, Melbourne, Victoria, Australia.
authors.forename: Fabricio
authors.initials: F
authors.lastname: da Silva Costa
authors.affiliation: Monash Ultrasound for Women, Melbourne, Victoria, Australia.
authors.forename: Simon
authors.initials: S
authors.lastname: Meagher
authors.affiliation: Women's Ultrasound, Melbourne, Victoria, Australia.|Royal Women's Hospital, Melbourne, Victoria, Australia.
authors.forename: Debbie L
authors.initials: DL
authors.lastname: Nisbet
authors.affiliation: Sydney Ultrasound for Women, Sydney, New South Wales, Australia.|University of New South Wales, Sydney, New South Wales, Australia.
authors.forename: Fergus
authors.initials: F
authors.lastname: Scott
mesh_terms: D000328:Adult; D000782:Aneuploidy; D001315:Australia; D025063:Chromosome Disorders / Q000175:diagnosis*; D002882:Chromosomes, Human, Pair 13; D002887:Chromosomes, Human, Pair 18; D041321:Chromosomes, Human, X; D041322:Chromosomes, Human, Y; D004314:Down Syndrome / Q000175:diagnosis; D005189:False Positive Reactions; D005260:Female; D005820:Genetic Testing / Q000379:methods* / Q000706:statistics & numerical data; D006801:Humans; D062145:Maternal Serum Screening Tests / Q000379:methods* / Q000706:statistics & numerical data; D008485:Medical Audit; D011237:Predictive Value of Tests; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011446:Prospective Studies; D012729:Sex Chromosome Aberrations; D014314:Trisomy / Q000175:diagnosis; D000073839:Trisomy 13 Syndrome; D000073842:Trisomy 18 Syndrome; D016216:Ultrasonography, Prenatal / Q000379:methods* / Q000706:statistics & numerical data
keywords: NIPT; cell-free DNA; chromosome abnormality; prenatal; screening; ultrasound