A new, noninvasive technology developed in France to test fetal Rhesus D (RhD) status performed well in a sample of pregnant women, according to findings recently published in Vox Sanguinis.
Hemolytic disease of the fetus and newborn (HDFN) develops when a mismatch between proteins found on fetal and maternal red blood cells cause the mother’s immune system to produce antibodiesAntibody A protein made by the immune system that recognizes and attacks foreign substances, such as bacteria, or in HDFN, fetal red blood cells carrying incompatible antigens. that attack the fetal blood cells. In some cases, HDFN results when a mother who is negative for the RhD protein produces antibodies against an RhD-positive fetus’ red blood cells.
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Currently, the CNRHP, France’s national center for perinatal blood disorders, uses the Free DNA fetal kit RHD to detect HDFN. However, in 7% of cases, the mother or fetus has variants in the RHD gene that interfere with the test. Therefore, the authors developed the FetoGnost® Kit RHD to improve the accuracy of non-invasive fetal RHD genotyping by flagging these variants.
The researchers collected blood samples from 105 pregnant women, some of whom were alloimmunized against the RhD antigen. They then tested samples using the FetoGnost® Kit RHD and compared results to both the Free DNA fetal kit® RHD and newborn RhD status. The goal of the analysis was to determine whether the FetoGnost® Kit RHD minimizes the risk of obtaining false positives, which could lead to unnecessary treatment.
Read more about HDFN testing and diagnosis
Findings revealed 97.4% concordance between the Free DNA fetal kit® RHD and the FetoGnost Kit RHD, with no false positives identified. The FetoGnost Kit RHD had a sensitivity of 96%, meaning that 96% of RHD-positive fetuses correctly tested as such. Furthermore, all fetuses testing negative for the RHD gene were truly negative, and all fetuses testing positive were truly positive.
The assay also successfully identified mothers and fetuses whose RHD gene sequence could interfere with the accuracy of the test. Together with additional genetic tested as needed, the FetoGnost Kit RHD may improve diagnostic accuracy in HDFN by decreasing “the risk of providing an erroneous result for the fetus (false positive) and…inappropriate clinical-biological advice” for the mother, the researchers concluded.
