Selected article for: "cross reactivity and Ct value"
Author: Chantal B.F. Vogels; Anderson F. Brito; Anne Louise Wyllie; Joseph R Fauver; Isabel M. Ott; Chaney C. Kalinich; Mary E. Petrone; Marie-Louise Landry; Ellen F. Foxman; Nathan D. Grubaugh
Title: Analytical sensitivity and efficiency comparisons of SARS-COV-2 qRT-PCR assays
  • Document date: 2020_4_1
    • ID: 6mdimxnk_12
    Snippet: We detected amplification of nonspecific products (Ct values <40) from nasopharyngeal swabs collected prior to the COVID-19 pandemic for the CCDC-N (5/8, 62.5%), CCDC-ORF1 (2/8, 25%), 2019-nCoV_N2 (2/8, 25%), and 2019-nCoV_N3 (6/8, 75%; Fig. 3 ). Moreover, the Ct value ranges for SARS-CoV-2-negative samples overlapped with the Ct value ranges (~36-40) for the swabs spiked with 10 0 and 10 1 SARS-CoV-2 genome equivalents/μL ( Fig. 3 ). Our data i.....
    Document: We detected amplification of nonspecific products (Ct values <40) from nasopharyngeal swabs collected prior to the COVID-19 pandemic for the CCDC-N (5/8, 62.5%), CCDC-ORF1 (2/8, 25%), 2019-nCoV_N2 (2/8, 25%), and 2019-nCoV_N3 (6/8, 75%; Fig. 3 ). Moreover, the Ct value ranges for SARS-CoV-2-negative samples overlapped with the Ct value ranges (~36-40) for the swabs spiked with 10 0 and 10 1 SARS-CoV-2 genome equivalents/μL ( Fig. 3 ). Our data indicates that the background cross-reactivity that we observed may limit the ability to differentiate between true positives and negatives at SARS-CoV-2 concentrations at or below 10 virus genome equivalents/μL when using the CCDC-N, CCDC-ORF1, 2019-nCoV_N2, and 2019-nCoV_N3. In fact, the 2019-nCoV_N3 primer-probe set has been excluded from the US CDC assay due to these issues 12 . However, Casto et al. also compared several SARS-CoV-2 primer-probe sets by testing dilutions of clinical samples and they did not detect any cross-reactivity for the 2019-nCoV_N2 set 13 . The source of the background cross-reactivity is unclear at present, but it may be attributable to non-specific detection of other seasonal coronaviruses that were circulating in 2017.

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