Droplet PCR System Identifies Fetal Genetic Data

A new study describes a simple, accurate, and low risk blood test that can detect fetal blood group, sex, and genetic conditions from a maternal blood sample.

Developed by researchers at Plymouth University (United Kingdom), the new noninvasive fetal Rh blood group and D antigen (RhD) genotyping test can help prevent unnecessary administration of prophylactic anti-D to women carrying RHD-negative fetuses. The blood sample can be taken from the mother when she has her first appointment with a general practitioner (GP) or midwife at the early stages of pregnancy, negating the need for multiple appointments and making best use of healthcare resources.

A study to validate the new test, which is based on a novel droplet digital polymerase chain reaction (ddPCR) platform to detect the cell-free fetal DNA (cffDNA) fraction, found that dPCR demonstrated 100% sensitivity for both fetal sex determination and RHD genotyping. The test can also be carried out on mothers at risk of X-linked genetic recessive diseases, including hemophilia and Duchenne muscular dystrophy, as well as mothers at risk of hemolytic disease of the newborn. The study was published in the November 2015 issue of Clinical Chemistry.

“Use of dPCR for identification of fetal specific markers can reduce the occurrence of false-negative and inconclusive results, particularly when samples express high levels of background maternal cell-free DNA,” concluded senior author Prof. Neil Avent, PhD, of the Plymouth University School of Biomedical and Healthcare Sciences. “The technique represents a comparatively low-risk method for the early identification of a number of conditions, which in turn will aid earlier diagnosis and possible therapies to the potential benefit of both mother and child.”

ddPCR is based on water-oil emulsion droplet technology; a sample is fractionated into 20,000 nanoliter-sized droplets, serving essentially the same function as individual test tubes or wells in a PCR plate, albeit in a much smaller format. The massive sample partitioning is a key aspect of the ddPCR technology, enabling high-throughput digital PCR in a manner that uses lower sample and reagent volumes and reduces overall cost, while still maintaining the sensitivity and precision of current digital PCR systems.

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