Comparison of BKV quantification using a single automated nucleic acid extraction platform and 3 real-time PCR assays

Monitoring peripheral blood for evidence of BK viremia through quantitative real-time PCR testing is an important management tool that allows for interventions that prevent nephropathy in renal allograft patients. This study compared the performance of 3 different real-time PCR assays for BKV quantification including 2 noncommercial tests (a historical assay "PEP" and 1 with improved genotypic inclusivity "V3T3") and 1 using commercial reagents (Qiagen/artus, "artus") after nucleic acid extraction of plasma with a single automated instrument (QIAsymphony). The measurable ranges (log10 copies/mL) were 2.7 to at least 8.0 for PEP and 2.0 to at least 8.0 for artus and V3T3 assays. Limits of detection (copies/mL) were 189, 56, and 28 for PEP, V3T3, and artus, respectively. Correlation experiments demonstrated linearity with original quantification results, although values obtained for the PEP assay were generally lower than those obtained for the V3T3 or artus assay across the measuring range. V3T3 and artus values were more closely related, although artus values were generally lower. The 3 assays returned different values from clinical plasma samples, likely due in part to variances in calibration. Low BKV concentrations were quantifiable by V3T3 and artus assays in plasmas that were previously deemed negative by PEP. These data underscore the need for monitoring with a single test to enable appropriate management decisions, and they suggest that an international preparation would be useful in harmonizing quantification of BKV viremia.