RE: Covid / back to school16 Aug 2020 23:01
Evidently it is a contentious study - one of the authors has put the following comments on the JAMA article:
'We very much appreciate the attention this paper has received and the comments left by different readers.
Several readers have left comments on technical characteristics of the assay used to generate the reported data. While it is correct that the clinical application of the assay is for qualitative detection of SARS-CoV-2 RNA, the cycle threshold data reported in this study were gathered for research purposes. There are abundant data in the literature to support the use of cycle threshold values as a proxy for the level of viral RNA in a sample, including for SARS-CoV-2 (1-4). Indeed, the commenters questioning the assay generally agree that cycle threshold values should correlate with the level of viral RNA in the samples. Although as many readers have noted there are caveats to doing so, some clinicians have argued that cycle threshold data could be applied in medical decision making based on correlations between these values and severity of COVID-19 disease in adults (4).
The Abbott assay used in our clinical laboratory includes an internal control (non-viral) sequence with every sample. Additionally, every clinical run included a control sample with 1000 copies of SARS-CoV-2 RNA per well. There are known differences between the cycle threshold generated with the Abbott assay and other platforms used for clinical detection of SARS-CoV-2 RNA that lead to significantly lower cycle thresholds for the assay we used (5), which do not alter either the results of our study or their interpretation. Using a rough rule-of-thumb that a one logarithm difference in template RNA corresponds to 3.3 cycle thresholds, the reported median CT for the youngest age group of about 6 cycles would correspond to about 10^8 copies/mL, not 10^11 as one reader suggests. Such levels are not at all dissimilar to those reported from upper respiratory tract samples for other viruses (6).'
https://jamanetwork.com/journals/jamapediatrics/fullarticle/2768952#
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