Multiplexed analysis of circulating cell-free fetal nucleic acids for noninvasive prenatal diagnostic RHD testing.

Objective: The objective of the study was the evaluation of a novel multiplex assay to detect fetal Rh blood group D-antigen gene (RHD) loci in maternal plasma from RhD-negative, pregnant women.

Study Design: An RHD genotyping assay was designed to detect exons 4, 5, 7, and 10 and RHDΨ (pseudogene) of the RHD gene along with a Y chromosome-specific assay and a generic polymerase chain reaction amplification control. Plasma samples from 150 RhD-negative pregnant women were assayed for fetal RHD genotype using the MassARRAY system.

Results: The fetal RHD status of 148 of 150 samples (98.7%) was correctly classified; 86 (57.3%) and 62 (41.3%) were positive and negative, respectively.

Conclusion: This study demonstrates that noninvasive prenatal diagnostics with a single-reaction multiplexed assay is a viable path toward routine characterization of fetal RHD genotypes using circulating cell-free fetal DNA in maternal plasma on the MassARRAY system and is perhaps preferable to serologic testing as currently used clinically.