Comparison of two highly automated DNA extraction systems for quantifying Epstein-Barr virus in whole blood

Background: Optimal automated molecular methods are needed to monitor Epstein-Barr virus (EBV) infections in transplant recipients. Objectives: To compare the extraction of EBV DNA from whole blood using the COBAS Ampliprep (TM) and the MagNA Pure (TM) instruments (Roche) for quantifying EBV DNA by real-time PCR. Study design: EBV DNA content was determined on clinical samples extracted by both systems. Results: The detection limit was 2.16 log(10) copies/mL using the COBAS Ampliprep (TM) extraction system. Specificity was 100% and we saw no cross-contamination. Extraction was linear from 2.60 to 5.60 log(10) copies/mL. The intra-assay variation was 1.91% for 3.60, 2% for 4.60 and 4.51% for 5.60 log(10) copies/mL: inter-assay variation was 4.88%. Sixty-six samples were tested: 26 were positive and 28 were negative by both methods. One sample was MagNA Pure (TM) positive/COBAS Ampliprep (TM) negative (virus load 3.15 log(10) copies/mL)and 10 samples were MagNA Pure (TM) negative/COBAS Ampliprep (TM) positive (virus loads from 1.59 to 3.51 log(10) copies/mL) (P<0.0001). Both methods gave similar quantitative results (average difference 0.07 log(10) copies/mL) which were well correlated (r = 0.73, P<0.001). Conclusions: The COBAS Ampliprep (TM) extraction system is comparable to the MagNA Pure (TM) and offers a high reliability for extracting EBV DNA from whole blood. (C) 2008 Elsevier B.V. All rights reserved.