A recent study published in Vox Sanguinis demonstrated the efficacy of a noninvasive tool to genotype fetal blood group and platelet antigens, which can aid in the diagnosis of fetal and neonatal alloimmune thrombocytopenia (FNAIT).
“With timely detection, […] FNAIT can be successfully treated through appropriate monitoring and adequate medical care,” the authors wrote. “Therefore, maternal– fetal blood group and platelet antigen incompatibility should be determined in the early second trimester.”
Many countries currently use real-time quantitative polymerase chain reaction (RT-qPCR) for these purposes. However, this strategy presents multiple limitations: Background signals can make it difficult to interpret results, and RT-qPCR does not have a highly accurate method to confirm the presence of fetal DNA in the sample.
To mitigate these limitations, the researchers developed a digital droplet polymerase chain reaction (ddPCR) assay, a technology that can be used to detect a variety of blood groups and platelet antigens with a high level of sensitivity while reducing background signal.
Read more about FNAIT testing and diagnosis
The ddPCR assay targets five blood groups — RhD, RhE, Rhc, RhC and K1 — and two platelet antigens, HPA-1a and HPA-5b. FNAIT is caused by incompatibility between the maternal and fetal platelet antigens.
In their study, the researchers analyzed samples from 229 pregnant women presenting with alloimmunity between April 2022 and March 2023. Of the 250 samples processed, the test was successful in 246 instances, resulting in a success rate of 98.4%. Of the four unsuccessful tests, two were lost to follow-up, and two individuals had variants in the RHD gene that interfered with interpretation of results.
A second sample was required in ten instances to validate results, and a third sample was only needed for one individual. The analysis revealed 116 cases of incompatibility between the mother and fetus.
“In conclusion, our in-house-developed and validated ddPCR fetal blood group and platelet antigen typing assay demonstrated excellent real-world performance and is an improvement over RT-qPCR for determination of fetal blood group and platelet antigen genotypes in alloimmunized pregnant women,” the authors wrote.
