Converting to an international unit system improves harmonization of results for SARS-CoV-2 quantification: Results from multiple external quality assessments

Buchta, Christoph; Kollros, Dominik; Jovanović, Jovana; Huf, Wolfgang; Delatour, Vincent; Puchhammer‐Stöckl, Elisabeth; Mayerhofer, Maximilian; Müller, Mathias M.; Shenoy, Santosh; Griesmacher, Andrea; Aberle, Stephan W.; Görzer, Irene; Camp, Jeremy-V.

doi:10.1016/j.jcv.2022.105352

Cited by 5 publications

(3 citation statements)

References 21 publications

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“…Of note, however, we continue to utilize derivative‐of‐care calibrators for high‐throughput epidemiologic studies for SARS‐CoV‐2, research that does not require a clinical laboratory environment, per se, but still demands many of the same analytic principles and logistics. Recently published work has demonstrated advantages in cross‐laboratory precision with molecular calibration against primary WHO standard, 41 and such practices could be further updated/expanded through traceable secondary standards.…”

Section: Discussionmentioning

confidence: 99%

Internationally standardized respiratory viral load testing with limited resources: A derivative‐of‐care calibration strategy for SARS‐CoV‐2

Tao,

Chan,

Maris

et al. 2024

Influenza Resp Viruses

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IntroductionSARS‐CoV‐2 has demonstrated that, in targeted circumstances, viral quantification within respiratory specimens can valuably inform patient management, as well as research. Nevertheless, the pandemic has illustrated concomitant challenges for obtaining high‐quality (and broadly comparable) respiratory viral loads. This includes a critical need for standardization and calibration, even though the necessary resources may not always be available for emergent pathogens and non‐bloodstream specimens.MethodsTo these ends, we describe a novel strategy for implementing quantitative SARS‐CoV‐2 testing with International Unit‐based calibration. Earlier in the course of the pandemic—when analytic resources were far more limited—select residual SARS‐CoV‐2 positive specimens from routine care in our diagnostic laboratory were pooled to formulate a clinically realistic secondary standard of high volume and analyte concentration, which was cross‐calibrated to the primary SARS‐CoV‐2 standard of the World Health Organization.ResultsThe resultant calibrators were integrated into the original CDC RT‐qPCR assay for SARS‐CoV‐2, whose (now broadened) performance characteristics were defined to generate a test appropriate for both clinical and research use. This test allowed for the quantification of virus in respiratory specimens down to a validated lower limit of quantification of 103.4 IU/ml.ConclusionsBy self‐formulating calibrators from this derivative‐of‐care secondary standard, we successfully validated respiratory viral loads without the commercial availability (at that time) of quantitative assays or calibrators. As the SARS‐CoV‐2 pandemic continues to decline—and even beyond this pathogen—this strategy may be applicable for laboratories seeking to implement viral load testing for nontraditional specimen types despite limited resources.

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Section: Discussionmentioning

confidence: 99%

Internationally standardized respiratory viral load testing with limited resources: A derivative‐of‐care calibration strategy for SARS‐CoV‐2

Tao,

Chan,

Maris

et al. 2024

Influenza Resp Viruses

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“…In the context of EQAs, a positive effect on the harmonisation of results for SARS-CoV-2 quantification was also shown in practical implementation when Ct values were converted into standardised units. 49 …”

Section: Extra-eqa Services Of Eqa Providersmentioning

confidence: 99%

Design of external quality assessment schemes and definition of the roles of their providers in future epidemics

et al. 2023

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“…Ct values are imperfect theoretical intermediate values in the quantification of DNA molecules using real-time qPCR, which were often misinterpreted as quantitative results in SARS-CoV-2 RNA detection. In order to express the result as viral load or concentration in SI units, they must be converted to copies/mL or international units/mL using instrument-specific factors [9] , [10] , [11] . However, since this intermediate data provides the basis for a quantitative result, we consider the Ct value to be sufficiently suitable for an initial investigation of the usefulness of EQA reproducibility for evaluating SARS-CoV-2 NAAT systems intended for NPT/POCT use.…”

Section: Introductionmentioning

confidence: 99%

Classification of “Near-patient” and “Point-of-Care” SARS-CoV-2 Nucleic Acid Amplification Test Systems and a first approach to evaluate their analytical independence of operator activities

Buchta

Zeichhardt

Badrick

et al. 2023

Journal of Clinical Virology

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Converting to an international unit system improves harmonization of results for SARS-CoV-2 quantification: Results from multiple external quality assessments

Cited by 5 publications

References 21 publications

Internationally standardized respiratory viral load testing with limited resources: A derivative‐of‐care calibration strategy for SARS‐CoV‐2

Internationally standardized respiratory viral load testing with limited resources: A derivative‐of‐care calibration strategy for SARS‐CoV‐2

Design of external quality assessment schemes and definition of the roles of their providers in future epidemics

Classification of “Near-patient” and “Point-of-Care” SARS-CoV-2 Nucleic Acid Amplification Test Systems and a first approach to evaluate their analytical independence of operator activities

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