Validation of the QIAsymphony RGQ system for DNA quantitation of different BK virus genotypes in whole blood samples

Human polyomavirus BK (BKV) is increasingly recognized as an opportunistic pathogen in transplant recipients. The aim of this work was to evaluate the artus® BK Virus QS-RGQ assay on the QIAsymphony RGQ system in whole blood (WB) samples (tests performed in an off-label capacity) according to different BKV genotypes by comparison with a laboratory-developed assay. BKV loads were measured in 111 WB samples and BKV genotype was determined by sequencing the full-length VP1 gene. The artus® assay exhibited a limit of detection of 77 copies/mL, a linearity range from 3.0 to 6.0 log10 copies/mL, intra-assay and inter-assay coefficients of variation ranging from 0.65% to 5.18%. Regarding BKV quantitation, artus® and laboratory-developed assays were highly correlated (Spearman correlation coefficient Rho = 0.79; P < 0.0001) with an excellent overall agreement (96.4%) and no significant quantitative difference according to Bland-Altman analysis (mean difference: −0.34 log10 copies/mL). The results did not show any influence of BKV genotype on BKV quantitation by the artus® assay, except a potential underquantitation of BKV subtype Ia which deserves further confirmation. In conclusion, the QIAsymphony RGQ system appears to be appropriate for the quantitation of BKV load in WB samples.