Evaluation of a BK virus viral load assay using the QIAGEN Artus BK Virus RG PCR test

Background: Viral load testing for BK Virus (BKV) has become the standard of care for the diagnosis of infection and monitoring of therapy of kidney transplant patients infected with BKV. However, there are currently no FDA-approved BKV quantification assays and no standardization among available tests. Objective and study design: This study evaluated the performance of the Artus BK Virus RG PCR (RUO) assay (QIAGEN) for accuracy, linearity, precision, analytical sensitivity, specificity, and correlation with a referral laboratory test in patient samples. Results: Linear regression analysis of the quantitative results demonstrated a linear range of quantification from 192 to 194 million (2.28 to 8.29 log(10)) DNA copies/mL and a coefficient of determination (R-2) of 0.994. A dilution series demonstrated a limit of detection and a limit of quantification of 2.00 log(10), and 2.30 log(10) copies/mL (>95% positivity rate), respectively. The precision of the assay was highly reproducible among runs with coefficients of variance (CV) ranging from 0.2% to 7.0%. A comparison of 34 matched samples showed a good agreement (R-2 = 0.983) between the Artus BK test and the referral laboratory results, with an average positive bias (0.39 log(10) copies/mL). Genotyping analysis using large-T antigen sequences demonstrated that 90% of the positive samples were BKV type I, and that there was no significant difference in quantification between the referral laboratory and Artus BK Virus tests. Conclusions: The Artus BK Virus RG PCR test is a reliable and sensitive assay for BKV DNA quantification as compared to the referral laboratory test. (C) 2012 Elsevier B. V. All rights reserved.