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Keywords:

  • fetal RHD determination;
  • cell-free fetal DNA;
  • psi-pseudogene;
  • SRY;
  • DBY;
  • TTTY2;
  • TGIF;
  • Sequenom Center for Molecular Medicine Laboratory Developed Test

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.

Conclusion

Fetal RHD genotyping can accurately be determined using ccff DNA in the first and second trimesters of pregnancy. Copyright © 2011 John Wiley & Sons, Ltd.