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

Background: Rapid, high throughput extraction systems are needed to monitor viral infections in immunosuppressed patients.

Objectives: Evaluate 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 Design: Compare 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.

Results: All 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 log(10)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 log(10)copies/ml) and BK virus (-0.24 log(10)copies/ml) while that of Epstein-Barr virus was slightly lower (1.02 log(10)copies/ml).

Conclusions: The MagNA Pure 96™ instrument is an easy-to-use, reliable high throughput platform for extracting nucleic acid from clinical whole blood specimens.