EasyCOV : LAMP based rapid detection of SARS-CoV-2 in saliva

Abstract

Covid-19 crisis showed us that rapid massive virus detection campaign is a key element in SARS-CoV-2 pandemic response. The classical RT-PCR laboratory platforms must be complemented with rapid and simplified technologies to enhance efficiency of large testing strategies. To this aim, we developed EasyCoV, a direct saliva RT-LAMP based SARS-CoV-2 virus detection assay that do not requires any RNA extraction step. It allows robust and rapid response under safe and easy conditions for healthcare workers and patients. EasyCov test was assessed under double blind clinical conditions (93 asymptomatic healthcare worker volonteers, 10 actively infected patients, 20 former infected patients tested during late control visit). EasyCov results were compared with classical laboratory RT-PCR performed on nasopharyngeal samples. Our results show that compared with nasopharyngeal laboratory RT-PCR, EasyCov SARS-CoV-2 detection test has a sensitivity of 72.7%. Measured on healthcare worker population the specificity was 95.7%. LAMP technology on saliva is clearly able to identify subjects with infectivity profile. Among healthcare worker population Easycov test detected one presymptomatic subject. Because it is simple, rapid and painless for patients, EasyCov saliva SARS-Cov-2 detection test may be useful for large screening of general population.

Diagnostic Salivary Tests for SARS-CoV-2

“…The results can be read by observing the color of the sample inside the test tube. A color change from orange to yellow indicates that the sample is positive and SARS-CoV-2 is present ( L’Helgouach et al 2020 ).…”

Use of the variplex™ SARS-CoV-2 RT-LAMP as a rapid molecular assay to complement RT-PCR for COVID-19 diagnosis

“…There are several studies that demonstrated satisfying sensitivity and specificity of RT-LAMP for SARS-CoV-2 detection but little is known about its performance of testing clinical samples directly without RNA extraction [ [11] , [12] , [13] , [14] ]. In this study we evaluated the newly introduced CE-labeled variplex™ SARS-CoV-2 LAMP assay and compared the clinical performance with commercial RT-PCR tests.…”

“…For a rapid diagnosis of SARS-CoV-2 cost-effective methods with low hands-on time that circumvent limitations of RT-PCR may be helpful tools for a routine diagnostic workflow [ 9 , 11 ]. RT-loop-mediated isothermal amplification (LAMP) may offer the possibility to be established as an alternative diagnostic technique [ [12] , [13] , [14] ]. The combination of RT with Bst polymerase possessing a DNA strand displacement activity allows amplification of target genes at a constant temperature in less than one hour.…”

Saliva TwoStep for rapid detection of asymptomatic SARS-CoV-2 carriers

“…Stabilizing saliva: Liberating RNA genomes from virions, protecting RNA from degradation, and dealing with pH variability in human saliva Multiple studies have developed methods for using saliva samples in combination with RT-LAMP specifically with a colorimetric readout (Lalli et al, 2020;L'Helgouach et al, 2020; Rabe and Cepko, 2020). However, the inherent variance in the acidity of saliva samples in a population, which can vary between 6.8 and 7.4 (Cameron et al, 2015), poses a significant problem because the colorimetric readout for RT-LAMP is pH-dependent.…”