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. 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.