Commutability of the First World Health Organization International Standard for Human Cytomegalovirus.
Quantitative detection of cytomegalovirus (CMV) DNA has become a standard part of care for many groups of immunocompromised patients; recent development of the first WHO international standard for human CMV DNA has raised hopes of reducing interlaboratory variability of results. Commutability of reference material has been shown to be necessary if such material is to reduce variability among laboratories. Here we evaluated the commutability of the WHO standard using 10 different real-time quantitative CMV PCR assays run by eight different laboratories. Test panels, including aliquots of 50 patient samples (40 positive samples and 10 negative samples) and lyophilized CMV standard, were run, with each testing center using its own quantitative calibrators, reagents, and nucleic acid extraction methods. Commutability was assessed both on a pairwise basis and over the entire group of assays, using linear regression and correspondence analyses. Commutability of the WHO material differed among the tests that were evaluated, and these differences appeared to vary depending on the method of statistical analysis used and the cohort of assays included in the analysis. Depending on the methodology used, the WHO material showed poor or absent commutability with up to 50% of assays. Determination of commutability may require a multifaceted approach; the lack of commutability seen when using the WHO standard with several of the assays here suggests that further work is needed to bring us toward true consensus.
Department of Pathology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA Randall.Hayden@stjude.org.
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Hayden
University of Alberta, Edmonton, Alberta, Canada.
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Preiksaitis
University of Alberta, Edmonton, Alberta, Canada.
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Tong
University of Alberta, Edmonton, Alberta, Canada Provincial Laboratory for Public Health, Edmonton, Alberta, Canada.
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Pang
Department of Biostatistics, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.
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Sun
Department of Biostatistics, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.
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Tang
Department of Laboratory Medicine, University of Washington, Seattle, Washington, USA.
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Cook
Department of Biostatistics, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.
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Pounds
National Institute for Biological Standards and Control, Potters Bar, United Kingdom.
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Fryer
Department of Medicine, Alpert Medical School of Brown University, Providence, Rhode Island, USA.
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Caliendo
D003587:Cytomegalovirus / Q000302:isolation & purification*; D003586:Cytomegalovirus Infections / Q000175:diagnosis* / Q000821:virology; D006801:Humans; D012015:Reference Standards; D015203:Reproducibility of Results; D019562:Viral Load / Q000379:methods* / Q000592:standards*; D014944:World Health Organization