title: DNA sequencing of maternal plasma to detect Down syndrome: an international clinical validation study.
abstract: OBJECTIVE
  Prenatal screening for Down syndrome has improved, but the number of resulting invasive diagnostic procedures remains problematic. Measurement of circulating cell-free DNA in maternal plasma might offer improvement.
  
  
  METHODS
  A blinded, nested case-control study was designed within a cohort of 4664 pregnancies at high risk for Down syndrome. Fetal karyotyping was compared with an internally validated, laboratory-developed test based on next-generation sequencing in 212 Down syndrome and 1484 matched euploid pregnancies. None had been previously tested. Primary testing occurred at a CLIA-certified commercial laboratory, with cross validation by a CLIA-certified university laboratory.
  
  
  RESULTS
  Down syndrome detection rate was 98.6% (209/212), the false-positive rate was 0.20% (3/1471), and the testing failed in 13 pregnancies (0.8%); all were euploid. Before unblinding, the primary testing laboratory also reported multiple alternative interpretations. Adjusting chromosome 21 counts for guanine cytosine base content had the largest impact on improving performance.
  
  
  CONCLUSIONS
  When applied to high-risk pregnancies, measuring maternal plasma DNA detects nearly all cases of Down syndrome at a very low false-positive rate. This method can substantially reduce the need for invasive diagnostic procedures and attendant procedure-related fetal losses. Although implementation issues need to be addressed, the evidence supports introducing this testing on a clinical basis.
authors: Division of Medical Screening and Special Testing, Department of Pathology and Laboratory Medicine, Women & Infants Hospital, Alpert Medical School of Brown University, Providence, Rhode Island 02903, USA. gpalomaki@ipmms.org
authors: Glenn E
authors: GE
authors: Palomaki
authors: Edward M
authors: EM
authors: Kloza
authors: Geralyn M
authors: GM
authors: Lambert-Messerlian
authors: James E
authors: JE
authors: Haddow
authors: Louis M
authors: LM
authors: Neveux
authors: Mathias
authors: M
authors: Ehrich
authors: Dirk
authors: D
authors: van den Boom
authors: Allan T
authors: AT
authors: Bombard
authors: Cosmin
authors: C
authors: Deciu
authors: Wayne W
authors: WW
authors: Grody
authors: Stanley F
authors: SF
authors: Nelson
authors: Jacob A
authors: JA
authors: Canick
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D004311:Double-Blind Method; D004314:Down Syndrome / Q000097:blood / Q000175:diagnosis* / Q000235:genetics; D005189:False Positive Reactions; D005260:Female; D005315:Fetal Diseases / Q000097:blood / Q000175:diagnosis* / Q000235:genetics; D006801:Humans; D007621:Karyotyping; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D017422:Sequence Analysis, DNA / Q000379:methods*