Rapid Isothermal Amplification for the Buccal Detection SARS-CoV-2 in the Context of Out-Patient COVID-19 Screening

• Main Authors: Amar Bouam, Jean-Jacques Vincent, Elisabeth Le Glass, Lionel Almeras, Pierre-Yves Levy, Hervé Tissot-Dupont, Jean-Christophe Lagier, Pierre-Edward Fournier, Didier Raoult, Michel Drancourt
• Format: Article
• Language: English
• Published: MDPI AG 2021-06-01
• Series: Journal of Clinical Medicine
• Subjects: SARS-CoV-2; COVID-19; point of care; diagnosis; saliva; isothermal amplification
• Online Access: https://www.mdpi.com/2077-0383/10/12/2643

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.