title: Non-invasive prenatal assessment of trisomy 21 by multiplexed maternal plasma DNA sequencing: large scale validity study.
abstract: OBJECTIVE
  To validate the clinical efficacy and practical feasibility of massively parallel maternal plasma DNA sequencing to screen for fetal trisomy 21 among high risk pregnancies clinically indicated for amniocentesis or chorionic villus sampling.
  
  
  METHODS
  Diagnostic accuracy validated against full karyotyping, using prospectively collected or archived maternal plasma samples.
  
  
  METHODS
  Prenatal diagnostic units in Hong Kong, United Kingdom, and the Netherlands.
  
  
  METHODS
  753 pregnant women at high risk for fetal trisomy 21 who underwent definitive diagnosis by full karyotyping, of whom 86 had a fetus with trisomy 21. Intervention Multiplexed massively parallel sequencing of DNA molecules in maternal plasma according to two protocols with different levels of sample throughput: 2-plex and 8-plex sequencing.
  
  
  METHODS
  Proportion of DNA molecules that originated from chromosome 21. A trisomy 21 fetus was diagnosed when the z score for the proportion of chromosome 21 DNA molecules was >3. Diagnostic sensitivity, specificity, positive predictive value, and negative predictive value were calculated for trisomy 21 detection.
  
  
  RESULTS
  Results were available from 753 pregnancies with the 8-plex sequencing protocol and from 314 pregnancies with the 2-plex protocol. The performance of the 2-plex protocol was superior to that of the 8-plex protocol. With the 2-plex protocol, trisomy 21 fetuses were detected at 100% sensitivity and 97.9% specificity, which resulted in a positive predictive value of 96.6% and negative predictive value of 100%. The 8-plex protocol detected 79.1% of the trisomy 21 fetuses and 98.9% specificity, giving a positive predictive value of 91.9% and negative predictive value of 96.9%.
  
  
  CONCLUSIONS
  Multiplexed maternal plasma DNA sequencing analysis could be used to rule out fetal trisomy 21 among high risk pregnancies. If referrals for amniocentesis or chorionic villus sampling were based on the sequencing test results, about 98% of the invasive diagnostic procedures could be avoided.
authors.affiliation: Centre for Research into Circulating Fetal Nucleic Acids, Li Ka Shing Institute of Health Sciences, Department of Chemical Pathology, The Chinese University of Hong Kong, Hong Kong SAR, China.
authors.forename: Rossa W K
authors.initials: RW
authors.lastname: Chiu
authors.forename: Ranjit
authors.initials: R
authors.lastname: Akolekar
authors.forename: Yama W L
authors.initials: YW
authors.lastname: Zheng
authors.forename: Tak Y
authors.initials: TY
authors.lastname: Leung
authors.forename: Hao
authors.initials: H
authors.lastname: Sun
authors.forename: K C Allen
authors.initials: KC
authors.lastname: Chan
authors.forename: Fiona M F
authors.initials: FM
authors.lastname: Lun
authors.forename: Attie T J I
authors.initials: AT
authors.lastname: Go
authors.forename: Elizabeth T
authors.initials: ET
authors.lastname: Lau
authors.forename: William W K
authors.initials: WW
authors.lastname: To
authors.forename: Wing C
authors.initials: WC
authors.lastname: Leung
authors.forename: Rebecca Y K
authors.initials: RY
authors.lastname: Tang
authors.forename: Sidney K C
authors.initials: SK
authors.lastname: Au-Yeung
authors.forename: Helena
authors.initials: H
authors.lastname: Lam
authors.forename: Yu Y
authors.initials: YY
authors.lastname: Kung
authors.forename: Xiuqing
authors.initials: X
authors.lastname: Zhang
authors.forename: John M G
authors.initials: JM
authors.lastname: van Vugt
authors.forename: Ryoko
authors.initials: R
authors.lastname: Minekawa
authors.forename: Mary H Y
authors.initials: MH
authors.lastname: Tang
authors.forename: Jun
authors.initials: J
authors.lastname: Wang
authors.forename: Cees B M
authors.initials: CB
authors.lastname: Oudejans
authors.forename: Tze K
authors.initials: TK
authors.lastname: Lau
authors.forename: Kypros H
authors.initials: KH
authors.lastname: Nicolaides
authors.forename: Y M Dennis
authors.initials: YM
authors.lastname: Lo
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D004247:DNA / Q000097:blood; D004314:Down Syndrome / Q000175:diagnosis*; D005260:Female; D006801:Humans; D007621:Karyotyping / Q000379:methods; D008297:Male; D008423:Maternal Age; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000379:methods*; D012372:ROC Curve; D012680:Sensitivity and Specificity; D017422:Sequence Analysis, DNA / Q000379:methods*; D019849:Sex Determination Processes
chemical_list: D004247:DNA