title: Fetal RHD genotype detection from circulating cell-free fetal DNA in maternal plasma in non-sensitized RhD negative women.
abstract: OBJECTIVE
  To examine the performance of the SensiGene Fetal RHD Genotyping Laboratory Developed Test (RHD Genotyping LDT) using circulating cell-free fetal DNA (ccff DNA) extracted from maternal plasma.
  
  
  METHODS
  ccff DNA was extracted from maternal blood from non-sensitized women with singleton pregnancies in two cohorts, one with a serotype reference (11-13 weeks' gestation) and one with the reference source (6-30 weeks' gestation). The presence of three RHD exon sequences (exons 4, 5, 7), the psi-pseudogene, three Y-chromosome sequences (SRY, DBY and TTTY2), and the X/Y-chromosome TGIF gene control were determined using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry-the RHD Genotyping LDT.
  
  
  RESULTS
  The cohort with a serotype RhD reference showed correct classification in 201 of 207 patients, a test accuracy of 97.1%, with a sensitivity and specificity for prediction of RhD serotype of 97.2 and 96.8%, respectively. The cohort with a genotype RHD reference showed correct classification in 198 of 199 patients, indicating a test accuracy of 99.5% with a sensitivity and specificity for prediction of RHD genotype of 100.0 and 98.3%, respectively.
  
  
  CONCLUSIONS
  Fetal RHD genotyping can accurately be determined using ccff DNA in the first and second trimesters of pregnancy.
authors.affiliation: Sequenom Center for Molecular Medicine, 3595 John Hopkins Ct, San Diego, CA 92106, USA. Allan@SCMMLab.com
authors.forename: Allan T
authors.initials: AT
authors.lastname: Bombard
authors.forename: Ranjit
authors.initials: R
authors.lastname: Akolekar
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Farkas
authors.forename: Anna L
authors.initials: AL
authors.lastname: VanAgtmael
authors.forename: Frank
authors.initials: F
authors.lastname: Aquino
authors.forename: Paul
authors.initials: P
authors.lastname: Oeth
authors.forename: Kypros H
authors.initials: KH
authors.lastname: Nicolaides
mesh_terms: D001787:Blood Group Incompatibility / Q000175:diagnosis*; D004247:DNA / Q000097:blood / Q000737:chemistry*; D005240:Feasibility Studies; D005260:Female; D005333:Fetus; D005838:Genotype; D006801:Humans; D011247:Pregnancy; D012204:Rh-Hr Blood-Group System / Q000235:genetics*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D012204:Rh-Hr Blood-Group System; C026410:Rho(D) antigen; D004247:DNA