A new highly automated extraction system for quantitative real-time PCRs from whole blood samples: Routine monitoring of opportunistic infections in immunosuppressed patients

BackgroundRapid, high throughput extraction systems are needed to monitor viral infections in immunosuppressed patients.ObjectivesEvaluate the performance of the MagNA Pure 96™ extraction system, and compare it to the COBAS Ampliprep™ for quantitative real-time PCR from whole blood samples.Study designCompare the MagNA Pure LC™, COBAS Ampliprep™ and MagNA Pure 96™ using ten-fold dilutions of blood samples containing cytomegalovirus. Evaluate analytical performances of the MagNA Pure 96™ from test samples containing cytomegalovirus. Evaluate clinical performances from 209 blood samples collected prospectively, extracted with the COBAS Ampliprep™ and the MagNA Pure 96™ systems and tested for cytomegalovirus, Epstein–Barr, BK and JC viruses.ResultsAll three extraction systems gave similar results with dilutions of a cytomegalovirus-positive sample. Analytical tests showed that the limit of detection was 500 copies/ml, specificity was 100%, with no cross-contamination. Quantification was linear from 3.0 to 6.0 log10 copies/ml. Intra-assay variation was 8.3–0.9% and inter-assay variation 8.8–5.2%. Clinical specimens extracted with the MagNA Pure 96™ and COBAS Ampliprep™ instruments agreed well for cytomegalovirus (r = 0.54; p = 0.07), Epstein–Barr virus (0.69; p = 0.0005) and BK virus (0.85; p = 0.01). All 55 samples were negative for JC virus. Mean loads were similar for cytomegalovirus (0.17 log10 copies/ml) and BK virus (−0.24 log10 copies/ml) while that of Epstein–Barr virus was slightly lower (1.02 log10 copies/ml).ConclusionsThe MagNA Pure 96™ instrument is an easy-to-use, reliable high throughput platform for extracting nucleic acid from clinical whole blood specimens.