High throughput non-invasive determination of foetal Rhesus D status using automated extraction of cell-free foetal DNA in maternal plasma and mass spectrometry

To examine the potential high throughput capability and efficiency of an automated DNA extraction system in combination with mass spectrometry for the non-invasive determination of the foetal Rhesus D status. A total of 178 maternal plasma samples from RHD-negative pregnant women were examined, from which DNA was extracted using the automated Roche MagNA Pure (TM) system. Presence of the foetal RHD gene was detected by PCR for RHD exon 7 and subsequent analysis using the Sequenom MassArray (TM) mass spectrometric system. We determined that as little as 15 pg of RHD-positive genomic DNA could be detected in a background of 585 pg of RHD-negative genomic DNA. The analysis of the clinical samples yielded a sensitivity and specificity of 96.1 and 96.1%, respectively. Our study indicated that automated DNA extraction in combination with mass spectrometry permits the determination of foetal Rhesus D genotype with an accuracy comparable to the current approaches using real-time PCR.