Multicenter Evaluation of a Commercial Cytomegalovirus Quantitative Standard: Effects of Commutability on Interlaboratory Concordance

Departments of Pathology, St. Jude Children's Research Hospital, Memphis, TN.
Journal of clinical microbiology (Impact Factor: 3.99). 09/2013; 51(11). DOI: 10.1128/JCM.02036-13
Source: PubMed


Commutability of quantitative reference materials has proven important for reliable and accurate results in clinical chemistry. As international reference standards and commercially produced calibration material have become available to address the variability of viral load assays, the degree to which such materials are commutable and the effect of commutability on assay concordance have been questioned. To investigate this, 60 archived clinical plasma samples, previously tested positive for cytomegalovirus (CMV) were retested by five different laboratories, each using a different quantitative CMV PCR assay. Results from each laboratory were calibrated both with lab-specific quantitative CMV standards (Lab Standards) and with common, commercially available standards (CMV Panel). Pairwise analyses among laboratories were performed using mean results from each clinical sample, calibrated first with Lab Standards and then with the CMV Panel. Commutability of the CMV Panel was determined based on difference plots for each laboratory pair showing plotted values of standards that were within the 95% prediction intervals for the clinical specimens. Commutability was demonstrated for 6 of 10 laboratory pairs using the CMV Panel. In half of these pairs, use of the CMV Panel improved quantitative agreement compared to use of Lab Standards. Two of four laboratory pairs for which the CMV Panel was non-commutable showed reduced quantitative agreement when that panel was used as a common calibrator. Commutability of calibration material varies across different quantitative PCR methods. Use of a common, commutable quantitative standard can improve agreement across different assays; use of a non-commutable calibrator can reduce agreement among laboratories.

Full-text preview

Available from:
  • [Show abstract] [Hide abstract]
    ABSTRACT: Cytomegalovirus (CMV), a member of the Herpesviridae family, is worldwide distributed. After the primary infection, CMV induces a latent infection with possible reactivation(s). It is responsible for severe to life-threatening diseases in immunocompromised patients and in foetuses and newborns of infected mothers. For monitoring CMV load, classical techniques based on rapid culture or pp65 antigenemia are progressively replaced by quantitative nuclear acid tests (QNAT), easier to implement and standardize. A large variety of QNAT are available from laboratory-developed assays to fully-automated commercial tests. The indications of CMV quantification include CMV infection during pregnancy and in newborns, and viral surveillance of grafted and non-grafted immunocompromised patients, patients with bowel inflammatory diseases and those hospitalised in intensive care unit. A close cooperation between virologists and clinicians is essential for optimizing the benefit of CMV DNA monitoring.
    No preview · Article · Dec 2013 · Expert Review of Anti-infective Therapy
  • [Show abstract] [Hide abstract]
    ABSTRACT: The recent development of the 1st WHO International Standard for human cytomegalovirus (CMV) and introduction of commercially produced secondary standards has raised hopes of improved agreement among laboratories performing quantitative CMV PCR. However, data are lacking to evaluate the trueness and uniformity of secondary standards and the consistency of results achieved when these materials are run on various assays. Three concentrations of each of three commercially prepared secondary CMV standards were tested in quadruplicate by three real-time and two digital PCR methods. Mean results were compared in a pairwise fashion with nominal values provided by each manufacturer. Agreement of results among all methods was also assessed for each sample and for like concentrations of each standard. The relationship between nominal values of standards and measured values varied depending upon assay used and manufacturer of standards, with the degree of bias ranging from +0.6 to -1.0 log10(IU/ml). The mean digital PCR result differed significantly among the secondary standards, as did the results of real-time PCR, particularly when plotted against nominal log10IU values. Commercially available quantitative secondary CMV standards produce variable results when tested by different real-time and digital PCR assays, with varying magnitudes of bias compared to nominal values. These findings suggest that the use of such materials may not achieve the intended uniformity among laboratories measuring CMV viral load, as envisioned by adaptation of the WHO standard. Copyright © 2015, American Society for Microbiology. All Rights Reserved.
    No preview · Conference Paper · Apr 2014
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The commutability of international reference standards is critical for ensuring quantitative agreement across different viral load assays. Here, we demonstrate the commutability of the Epstein-Barr virus (EBV) WHO international standard for the BamHI-W and artus EBV assays.
    Preview · Article · Jul 2014 · Journal of Clinical Microbiology
Show more