Photo Credit: Rasi Bhadramani
The following is a summary of “Clinical Validation of a Prenatal Cell-Free DNA Screening Test for Fetal RHD in a Large U.S. Cohort,” published in the November 2024 issue of Obstetrics and Gynecology by Thompson et al.
A noninvasive prenatal cell-free deoxyribonucleic acid (cfDNA) test was evaluated in pregnant individuals to identify fetal RHD status, supporting efforts to prevent RhD alloimmunization.
Researchers conducted a prospective study to validate a cfDNA test in pregnant individuals for fetal RhD status.
They assessed the accuracy of the next-generation sequencing-based cfDNA test in identifying fetal RHD status among 655 pregnant patients (74.0% White, 13.7% Hispanic, 7.0% Black, and 2.1% Asian), excluding dizygotic twin pregnancies. Samples were included if fetal and maternal RhD genotypes, RhD serology, and maternal RHD deletion or RHD-CE-D hybrid were available and were blinded to fetal RhD status during analysis.
The results showed the test correctly identified all 356 RhD-positive fetuses (sensitivity 100%, 95% CI, 98.9–100%). Among the 297 RhD-negative fetuses, 295 were accurately identified as RhD-negative (specificity 99.3%, 95% CI, 97.6–99.8%). The test also detected three cases with the fetal RhD pseudogene (RhDΨ) genotype.
They concluded that the cfDNA test enabled early and accurate identification of fetal RhD genotype starting at 9 weeks of pregnancy, supporting the prevention and management of RhD alloimmunization.
