title: Diagnostic accuracy of fetal rhesus D genotyping using cell-free fetal DNA during the first trimester of pregnancy.
abstract: BACKGROUND
  Rhesus D genotyping with cell-free fetal DNA currently is used throughout the world. Although this technique has spread rapidly, its optimal use is still a matter of debate. This screening test has been introduced mainly for the treatment of RhD-negative pregnant women during the third trimester of pregnancy, thereby avoiding systematic anti-D prophylaxis, yet such a strategy has proved cost-ineffective. Publications reporting on fetal RHD genotyping with cell-free DNA in maternal plasma, specifically during the first trimester of pregnancy, are scarce in the scientific literature.
  
  
  OBJECTIVE
  This study sought to assess the performance of noninvasive fetal Rhesus D genotyping in the first trimester of pregnancy with a single-exon real-time polymerase chain reaction assay.
  
  
  METHODS
  This was a retrospective observational multicenter study. Cell-free fetal DNA was extracted from maternal blood of both nonimmunized and immunized women at 10-14 weeks of gestation. RHD sequence was determined by quantitative polymerase chain reaction, with amplification of exon 10. Results were compared with RhD phenotype data that were obtained by cord blood sampling of neonates.
  
  
  RESULTS
  In total, 416 serum samples from RhD-negative pregnant women were collected during the first trimester of pregnancy. The test's overall sensitivity and specificity were 100% (95% confidence interval, 96.9-100.0) and 95.2% (95% confidence interval, 90.5-97.6), respectively. The negative and positive predictive values were 99.8% (95% confidence interval, 94.9-100.0) and 97.1% (95% confidence interval, 94.2-98.6), respectively. Fetal RHD status was inconclusive in 9 cases (2.2%).
  
  
  CONCLUSIONS
  Noninvasive fetal RHD determination by single-exon quantitative polymerase chain reaction during the first trimester of pregnancy exhibits high accuracy.
authors.affiliation: Service de Gynécologie-Obstétrique et Médecine de la Reproduction, Hôpital Antoine Béclère, Université Paris Sud, Clamart, France.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Vivanti
authors.affiliation: Service de Gynécologie-Obstétrique et Médecine de la Reproduction, Hôpital Antoine Béclère, Université Paris Sud, Clamart, France.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Benachi
authors.affiliation: Laboratoire de Biologie Médicale, Paris, France.
authors.forename: François-Xavier
authors.initials: FX
authors.lastname: Huchet
authors.affiliation: Service de Gynécologie-Obstétrique, Hôpital Necker-Enfants Malades, Paris, France.
authors.forename: Yves
authors.initials: Y
authors.lastname: Ville
authors.affiliation: Département Mère-Enfant, Institut Montsouris, Paris, France.
authors.forename: Henri
authors.initials: H
authors.lastname: Cohen
authors.affiliation: Département de Biologie Spécialisée et de Génétique, Laboratoire CERBA, Saint-Ouen l'Aumône, France. Electronic address: jmcosta@lab-cerba.com.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Costa
mesh_terms: D000328:Adult; D001787:Blood Group Incompatibility / Q000175:diagnosis* / Q000188:drug therapy; D004247:DNA / Q000097:blood*; D005091:Exons; D005260:Female; D005333:Fetus / Q000378:metabolism*; D060005:Genotyping Techniques; D006801:Humans; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D060888:Real-Time Polymerase Chain Reaction; D012189:Retrospective Studies; D012204:Rh-Hr Blood-Group System / Q000235:genetics*; D018029:Rho(D) Immune Globulin / Q000627:therapeutic use; D012680:Sensitivity and Specificity
chemical_list: C061961:RHO(D) antibody; D012204:Rh-Hr Blood-Group System; D018029:Rho(D) Immune Globulin; C026410:Rho(D) antigen; D004247:DNA
keywords: RHD genotyping; cell-free fetal DNA; maternal serum