title: Toward standardization of BK virus monitoring: evaluation of the BK virus R-gene kit for quantification of BK viral load in urine, whole-blood, and plasma specimens.
abstract: Screening of BK virus (BKV) replication is recommended to identify patients at increased risk of BKV-associated diseases. However, the heterogeneity of molecular techniques hinders the establishment of universal guidelines for BKV monitoring. Here we aimed to compare the performance of the CE-marked BK virus R-gene kit (R-gene) to the performance of our in-house assay for quantification of BKV DNA loads (BKVL). A 12-specimen panel from the Quality Control for Molecular Diagnostics (QCMD) organization, 163 urine samples, and 88 paired specimens of plasma and whole blood (WB) from transplant recipients were tested. Both the R-gene and in-house assays showed a good correlation within the QCMD panel (r = 0.995 and r = 0.989, respectively). BKVL were highly correlated between assays, although positive biases were observed with the in-house assay in analysis of urine (0.72 ± 0.83 log10 copies/ml), plasma (1.17 ± 0.63 log10 copies/ml), and WB (1.28 ± 0.37 log10 copies/ml). Recalibration with a common calibrator significantly reduced the bias in comparisons between assays. In contrast, BKVL was underestimated with the in-house PCR in eight samples containing BKV genotype II, presenting point mutations at primer-annealing sites. Using the R-gene assay, plasma and WB specimens were found to be equally suitable for quantification of BKVL, as indicated by the high correlation coefficient (r = 0.965, P < 0.0001). In conclusion, the R-gene assay demonstrated reliable performance and higher accuracy than the in-house assay for quantification of BKVL in urine and blood specimens. Screening of BKV replication by a well-validated commercial kit may enable clinical laboratories to assess viral loads with greater reproducibility and precision.
authors.affiliation: Laboratoire de Virologie, Hôpitaux Universitaires de Strasbourg, Strasbourg, France Inserm, U1109, LabEx TRANSPLANTEX, Strasbourg, France Fédération de Médecine Translationnelle de Strasbourg (FMTS), Université de Strasbourg, Strasbourg, France.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Sueur
authors.affiliation: Laboratoire de Virologie, Hôpitaux Universitaires de Strasbourg, Strasbourg, France Inserm, U1109, LabEx TRANSPLANTEX, Strasbourg, France Fédération de Médecine Translationnelle de Strasbourg (FMTS), Université de Strasbourg, Strasbourg, France.
authors.forename: Morgane
authors.initials: M
authors.lastname: Solis
authors.affiliation: Laboratoire de Virologie, Hôpitaux Universitaires de Strasbourg, Strasbourg, France Fédération de Médecine Translationnelle de Strasbourg (FMTS), Université de Strasbourg, Strasbourg, France.
authors.forename: Mariam
authors.initials: M
authors.lastname: Meddeb
authors.affiliation: Inserm, U1109, LabEx TRANSPLANTEX, Strasbourg, France Fédération de Médecine Translationnelle de Strasbourg (FMTS), Université de Strasbourg, Strasbourg, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Soulier
authors.affiliation: Inserm, U1109, LabEx TRANSPLANTEX, Strasbourg, France Fédération de Médecine Translationnelle de Strasbourg (FMTS), Université de Strasbourg, Strasbourg, France.
authors.forename: Pilar
authors.initials: P
authors.lastname: Domingo-Calap
authors.affiliation: Laboratoire de Virologie, Hôpitaux Universitaires de Strasbourg, Strasbourg, France Inserm, U1109, LabEx TRANSPLANTEX, Strasbourg, France Fédération de Médecine Translationnelle de Strasbourg (FMTS), Université de Strasbourg, Strasbourg, France.
authors.forename: Quentin
authors.initials: Q
authors.lastname: Lepiller
authors.affiliation: Laboratoire de Virologie, Hôpitaux Universitaires de Strasbourg, Strasbourg, France.
authors.forename: Rachel
authors.initials: R
authors.lastname: Freitag
authors.affiliation: Inserm, U1109, LabEx TRANSPLANTEX, Strasbourg, France Fédération de Médecine Translationnelle de Strasbourg (FMTS), Université de Strasbourg, Strasbourg, France.
authors.forename: Seiamak
authors.initials: S
authors.lastname: Bahram
authors.affiliation: Inserm, U1109, LabEx TRANSPLANTEX, Strasbourg, France Fédération de Médecine Translationnelle de Strasbourg (FMTS), Université de Strasbourg, Strasbourg, France Département de Néphrologie, Hôpitaux Universitaires de Strasbourg, Strasbourg, France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Caillard
authors.affiliation: Laboratoire de Virologie, Hôpitaux Universitaires de Strasbourg, Strasbourg, France Inserm, U1109, LabEx TRANSPLANTEX, Strasbourg, France Fédération de Médecine Translationnelle de Strasbourg (FMTS), Université de Strasbourg, Strasbourg, France.
authors.forename: Heidi
authors.initials: H
authors.lastname: Barth
authors.affiliation: Laboratoire de Virologie, Hôpitaux Universitaires de Strasbourg, Strasbourg, France Inserm, U1109, LabEx TRANSPLANTEX, Strasbourg, France Fédération de Médecine Translationnelle de Strasbourg (FMTS), Université de Strasbourg, Strasbourg, France.
authors.forename: Françoise
authors.initials: F
authors.lastname: Stoll-Keller
authors.affiliation: Laboratoire de Virologie, Hôpitaux Universitaires de Strasbourg, Strasbourg, France Inserm, U1109, LabEx TRANSPLANTEX, Strasbourg, France Fédération de Médecine Translationnelle de Strasbourg (FMTS), Université de Strasbourg, Strasbourg, France samira.fafi-kremer@unistra.fr.
authors.forename: Samira
authors.initials: S
authors.lastname: Fafi-Kremer
mesh_terms: D001739:BK Virus / Q000302:isolation & purification*; D001769:Blood / Q000821:virology*; D006801:Humans; D027601:Polyomavirus Infections / Q000821:virology*; D011933:Reagent Kits, Diagnostic; D015203:Reproducibility of Results; D014412:Tumor Virus Infections / Q000821:virology*; D014556:Urine / Q000821:virology*; D019562:Viral Load / Q000379:methods* / Q000592:standards*
chemical_list: D011933:Reagent Kits, Diagnostic