The power of digital PCR in fetal blood group genotyping: a review

Abstract

: There is a clinical need to determine the fetal blood group status for pregnant women who present with clinically significant red cell antibodies to optimize perinatal care. Non-invasive prenatal testing (NIPT) to assess the fetal blood group status is problematic for blood groups that arise from single nucleotide variants (SNVs) because the cell-free DNA from the maternal allele is present in greater abundance than the fetal allele, resulting in competition, especially in traditional real-time quantitative polymerase chain reaction (qPCR) platforms. This review discusses the power for digital (d)PCR to overcome this limitation. The dPCR is based on first diluting and compartmentalizing individual DNA molecules into individual PCR mixes, so that the competing (e.g., maternal) molecules are separated from the target (fetal) DNA molecule prior to amplification. In comparison to qPCR platforms, dPCR is amenable to the quantitation of a positive signal from an individual DNA molecule, providing the ability to calculate the fractional abundance of the fetal sequence of interest. Comparison studies, though small in number, show that dPCR is more precise and sensitive. Clinical feasibility studies to date show that dPCR for fetal Kell antigen, Rhc, RhE and Duffy antigens have high accuracy. The key limitation of the dPCR approach is that separate assays need to be established and validated for each blood group antigen. Despite that limitation, the power of dPCR for fetal blood group genotyping provides an added diagnostic tool in the management of women with red cell antibodies.