Abstract
A commercially available isothermal amplification of SARS-CoV-2 RNA was applied to self-collected saliva samples using dry dental cotton rolls, which were held in the mouth for two minutes. Of 212 tests, isothermal amplification yielded three (0.14%) invalid results, 120 (56.6%) positive results and 89 (42%) negative results. Compared to reference RT-PCR assays routinely performed simultaneously on nasopharyngeal swabs, excluding the three invalid isothermal amplification assays and one RT-PCR invalid assay, these figures indicated that 119/123 (96.7%) samples were positive in both methods and 85/85 samples were negative in both methods. Four positive buccal swabs which were missed by the isothermal amplification, exhibited Ct values of 26–34 in reference RT-PCR assays. Positive isothermal amplification detection was achieved in less than 10 min. Supervision of the self-sampling procedure was key to achieve these performances. These data support the proposal to use the protocol reported in this paper, including supervised buccal self-sampling, to screen people suspected of having COVID-19 at the point of care.
Highlights
Direct diagnosis of SARS-CoV-2 infection, referred as COVID-19 [1], is routinely performed by the reverse-transcription polymerase chain reaction (RT-PCR) detection of viralRNA in nasopharyngeal swabs [2,3], with results obtained in less than 25 min at the point of care (POC) [4,5]
Alternative posterior oropharyngeal saliva swabs were collected by an investigator and yielded similar detection rates of SARS-CoV-2 RNA as the nasopharyngeal swabs, suggesting that oral fluid could be of interest for the diagnosis of COVID-19 [6]
We evaluated the performance of one such commercially available isothermal molecular test for the rapid detection of SARS-CoV-2 RNA detection in standardized buccal self-collected samples in order to achieve unprecedented sensitivity and specificity of isothermal amplification of SARS-CoV-2 RNA detection, compared to the gold standard RT-PCR, in less than 10 min
Summary
Direct diagnosis of SARS-CoV-2 infection, referred as COVID-19 [1], is routinely performed by the reverse-transcription polymerase chain reaction (RT-PCR) detection of viral. Alongside RT-PCR, isothermal amplification recently emerged as an alternative technique for detecting SARS-CoV-2 RNA yet reports of its application to nasopharyngeal swabs yielded contradictory data regarding its clinical performance [13]. Among this emerging technology, loop-mediated amplification (LAMP) and Nicking enzyme-assisted reaction (NEAR). We evaluated the performance of one such commercially available isothermal molecular test for the rapid detection of SARS-CoV-2 RNA detection in standardized buccal self-collected samples in order to achieve unprecedented sensitivity and specificity of isothermal amplification of SARS-CoV-2 RNA detection, compared to the gold standard RT-PCR, in less than 10 min
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