Improvement in fetal DNA extraction from maternal plasma. Evaluation of the NucliSens magnetic extraction system and the QlAamp DSP virus kit in comparison with the QIAamp DNA blood mini kit

Objective Prenatal diagnostic assays have been developed using free fetal DNA circulating in the maternal blood of pregnant women. Efficient DNA extraction is crucial for a robust analysis. To improve fetal DNA yield, we tested two manual extraction methods-the NucliSens Magnetic Extraction (NMAG) system and the QIAamp DSP Virus Kit (QDSP)-against our current standard method, the widely used QIAamp DNA Blood Mini Kit QDNA). Methods The fetal DNA yield of the two extraction systems was evaluated using the RHD exon 7 as target in DNA extracts of 75 plasma samples from pregnant RhD-negative women, known to have given birth to RhD-positive infanto. The total DNA yield was evaluated in 23 samples, targeting GAPDH. Results The fetal DNA yield was improved by a mean factor of 1.7 using the NMAG system, and improved by a mean factor of 1.5 using the QDSP. The total DNA yield was improved by a mean factor of 2.3 using the NMAG system, and by a mean factor of 1.3 using the QDSP. Conclusion Both extraction systems tested were superior to our standard with regard to DNA yield. This improvement may have a great impact on the success of genotyping in early pregnancy. Copyright (C) 2007 John Wiley & Sons, Ltd.