Specific magnetic bead-based capture of free fetal DNA from maternal plasma.

An automated magnetic capture hybridization (MCH) method for the extraction and enrichment of fetal RHD specific DNA fragments from maternal plasma was developed using plasma from 1000 D-negative pregnant women. A real time PCR protocol for RHD exon 7 was applied. MCH was compared with the QIAamp DSP Virus Kit (QIAamp) as a reference. Compared with the QIAamp method, the percentage of fetal DNA increased from 2.86% to 4.83% (p < 0.05, n = 8). The 95% detection limit of MCH was determined at 286 pg/ml (43 geg/ml) compared with 138 pg/ml (21 geq/ml) for the QIAamp DSP Virus Kit.