title: Validation of targeted sequencing of single-nucleotide polymorphisms for non-invasive prenatal detection of aneuploidy of chromosomes 13, 18, 21, X, and Y.
abstract: OBJECTIVE
  To assess the performance of cell-free DNA (cfDNA) testing in maternal blood for detection of fetal aneuploidy of chromosomes 13, 18, 21, X, and Y using targeted sequencing of single-nucleotide polymorphisms.
  
  
  METHODS
  Prospective study in 242 singleton pregnancies undergoing chorionic villus sampling at 11 to 13 weeks. Maternal blood was collected before chorionic villus sampling and sent to Natera (San Carlos, CA, USA). cfDNA was isolated from maternal plasma, and targeted multiplex PCR amplification followed by sequencing of 19 488 polymorphic loci covering chromosomes 13, 18, 21, X, and Y was performed. Sequencing data were analyzed using the NATUS algorithm that determines the copy number and calculates a sample-specific accuracy for each of the five chromosomes tested. Laboratory personnel were blinded to fetal karyotype.
  
  
  RESULTS
  Results were provided for 229 (94.6%) of the 242 cases. Thirty-two cases were correctly identified as aneuploid, including trisomy 21 [n = 25; sensitivity = 100% (CI: 86.3-100%), specificity = 100% (CI: 98.2-100%)], trisomy 18 (n = 3), trisomy 13 (n = 1), Turner syndrome (n = 2), and triploidy (n = 1), with no false positive or false negative results. Median accuracy was 99.9% (range: 96.0-100%).
  
  
  CONCLUSIONS
  cfDNA testing in maternal blood using targeted sequencing of polymorphic loci at chromosomes 13, 18, 21, X, and Y holds promise for accurate detection of fetal autosomal trisomies, sex chromosome aneuploidies, and triploidy.
authors.affiliation: Harris Birthright Research Centre for Fetal Medicine, King's College Hospital, London, UK. kypros@fetalmedicine.com
authors.forename: K H
authors.initials: KH
authors.lastname: Nicolaides
authors.forename: A
authors.initials: A
authors.lastname: Syngelaki
authors.forename: M
authors.initials: M
authors.lastname: Gil
authors.forename: V
authors.initials: V
authors.lastname: Atanasova
authors.forename: D
authors.initials: D
authors.lastname: Markova
mesh_terms: D000293:Adolescent; D000328:Adult; D000782:Aneuploidy; D025063:Chromosome Disorders / Q000097:blood / Q000175:diagnosis* / Q000235:genetics; D002882:Chromosomes, Human, Pair 13 / Q000235:genetics; D002887:Chromosomes, Human, Pair 18 / Q000235:genetics; D002891:Chromosomes, Human, Pair 21 / Q000235:genetics; D041321:Chromosomes, Human, X / Q000235:genetics; D041322:Chromosomes, Human, Y / Q000235:genetics; D005260:Female; D006801:Humans; D008875:Middle Aged; D020641:Polymorphism, Single Nucleotide; D011247:Pregnancy / Q000097:blood; D011296:Prenatal Diagnosis / Q000379:methods*; D012680:Sensitivity and Specificity; D017422:Sequence Analysis, DNA / Q000379:methods*; D055815:Young Adult