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Progress in Quantitative Viral Load Testing: Variability and Impact of the WHO Quantitative International Standards. Journal of clinical microbiology Hayden, R. T., Sun, Y., Tang, L., Procop, G. W., Hillyard, D. R., Pinsky, B. A., Young, S. A., Caliendo, A. M. 2017; 55 (2): 423-430

Abstract

It has been hoped that the recent availability of WHO quantitative standards would improve interlaboratory agreement for viral load testing; however, insufficient data are available to evaluate whether this has been the case. Results from 554 laboratories participating in proficiency testing surveys for quantitative PCR assays of cytomegalovirus (CMV), Epstein-Barr virus (EBV), BK virus (BKV), adenovirus (ADV), and human herpesvirus 6 (HHV6) were evaluated to determine overall result variability and then were stratified by assay manufacturer. The impact of calibration to international units/ml (CMV and EBV) on variability was also determined. Viral loads showed a high degree of interlaboratory variability for all tested viruses, with interquartile ranges as high as 1.46 log10 copies/ml and the overall range for a given sample up to 5.66 log10 copies/ml. Some improvement in result variability was seen when international units were adopted. This was particularly the case for EBV viral load results. Variability in viral load results remains a challenge across all viruses tested here; introduction of international quantitative standards may help reduce variability and does so more or less markedly for certain viruses.

View details for DOI 10.1128/JCM.02044-16

View details for PubMedID 27852673

View details for PubMedCentralID PMC5277511