title: Increased fetal DNA concentrations in the plasma of pregnant women carrying fetuses with trisomy 21.
abstract: BACKGROUND
  The recent discovery of the presence of circulating cell-free fetal DNA in maternal plasma opens up new prenatal diagnostic applications and provides new avenues for clinical investigation. It is of research and potential diagnostic interest to determine whether fetal trisomy 21 may be associated with quantitative abnormalities of circulating fetal DNA in maternal plasma.
  
  
  METHODS
  Maternal plasma samples were prospectively collected from two centers situated in Hong Kong and Boston. Samples collected from Boston consisted of 7 women carrying male trisomy 21 fetuses, 19 carrying euploid male fetuses, and 13 carrying female fetuses. Samples collected from Hong Kong consisted of 6 women carrying male trisomy 21 fetuses, 18 carrying euploid male fetuses, and 10 carrying female fetuses. Male fetal DNA in maternal plasma was measured using real-time quantitative Y-chromosomal PCR.
  
  
  RESULTS
  For patients recruited from Boston, the median circulating fetal DNA concentrations in women carrying trisomy 21 and euploid male fetuses were 46.0 genome-equivalents/mL and 23.3 genome-equivalents/mL, respectively (P = 0.028). For patients recruited from Hong Kong, the median circulating fetal DNA concentrations in women carrying trisomy 21 and euploid male fetuses were 48.2 genome-equivalents/mL and 16.3 genome-equivalents/mL, respectively (P = 0.026). None of the samples from women carrying female fetuses had detectable Y-chromosomal signals.
  
  
  CONCLUSIONS
  Abnormally high concentrations of circulating fetal DNA are found in a proportion of women carrying fetuses with trisomy 21. The robustness and reproducibility of real-time PCR analysis of maternal plasma makes it a valuable tool for cross-institutional collaboration involving centers located in different parts of the world.
authors.affiliation: Department of Chemical Pathology, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, New Territories, Hong Kong SAR. loym@cuhk.edu.hk
authors.forename: Y M
authors.initials: YM
authors.lastname: Lo
authors.forename: T K
authors.initials: TK
authors.lastname: Lau
authors.forename: J
authors.initials: J
authors.lastname: Zhang
authors.forename: T N
authors.initials: TN
authors.lastname: Leung
authors.forename: A M
authors.initials: AM
authors.lastname: Chang
authors.forename: N M
authors.initials: NM
authors.lastname: Hjelm
authors.forename: R S
authors.initials: RS
authors.lastname: Elmes
authors.forename: D W
authors.initials: DW
authors.lastname: Bianchi
mesh_terms: D015415:Biomarkers / Q000097:blood; D004247:DNA / Q000097:blood*; D004314:Down Syndrome / Q000097:blood* / Q000235:genetics; D005260:Female; D005333:Fetus / Q000378:metabolism*; D006801:Humans; D008297:Male; D016133:Polymerase Chain Reaction; D011247:Pregnancy; D014998:Y Chromosome
chemical_list: D015415:Biomarkers; D004247:DNA