Detection of SARS-CoV-2 in saliva: implications for specimen transport and storage

Abstract

Saliva has recently been proposed as a suitable specimen for the diagnosis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Use of saliva as a diagnostic specimen may present opportunities for SARS-CoV-2 reverse transcription polymerase chain reaction (RT-PCR) testing in remote and low-resource settings. Determining the stability of SARS-CoV-2 RNA in saliva over time is an important step in determining optimal storage and transport times. We undertook an in vitro study to assess whether SARS-CoV-2 could be detected in contrived saliva samples. The contrived saliva samples comprised 10 ml pooled saliva spiked with gamma-irradiated SARS-CoV-2 to achieve a concentration of 2.58×104 copies ml SARS-CoV-2, which was subsequently divided into 2 ml aliquots comprising: (i) neat saliva; and a 1 : 1 dilution with (ii) normal saline; (iii) viral transport media, and (iv) liquid Amies medium. Contrived samples were made in quadruplicate, with two samples of each stored at either: (i) room temperature or (ii) 4 °C. SARS-CoV-2 was detected in all SARS-CoV-2 spiked samples at time point 0, day 1, 3 and 7 at both storage temperatures using the N gene RT-PCR assay and time point 0, day 1 and day 7 using the Xpert Xpress SARS-CoV-2 (Cepheid, Sunnyvale, USA) RT-PCR assay. The ability to detect SARS-CoV-2 in saliva over a 1 week period is an important finding that presents further opportunities for saliva testing as a diagnostic specimen for the diagnosis of SARS-CoV-2.

Wide Application of Minimally Processed Saliva on Multiple RT-qPCR Kits for SARS-CoV-2 Detection in Indonesia

“…One of the highlights of our study is that we also monitored the stability of saliva specimens and found it remained stable at cold (2-8°C) and room temperature in the laboratory (~25°C) for up to 5 days. Our finding is concordant with previous studies done by spiking SARS-CoV-2 into saliva specimens (Williams et al, 2021). SARS-CoV-2 may remain stable in saliva despite the presence of RNases in the medium due to its hard outer shell (Goh et al, 2020).…”

Wide application of minimally processed saliva on multiple RT-qPCR kits for SARS-CoV-2 detection in Indonesia

“…One of the highlights of our study is that we also monitored the stability of saliva specimens and found it remained stable at cold (2-8 o C) and room temperature in the laboratory (~25 o C) for up to 5 days. Our finding is concordant with previous studies done by spiking SARS-CoV-2 into saliva specimens (Williams et al, 2021). SARS-CoV-2 may remain stable in saliva despite the presence of RNases in the medium due to its hard outer shell (Goh et al, 2020).…”

Developing RT-LAMP Assays for Detection of SARS-CoV-2 in Saliva

“…Saliva testing is an attractive method for COVID-19 diagnosis. 1) It is a non-invasive method for sample collection; 2) saliva can be collected by a non-medical care worker, thus reducing the risk of nosocomial transmission; and 3) saliva is relatively stable at a broad range of storage temperatures 35,36 . Despite these advantages, there are also challenges facing COVID-19 saliva testing: 1) saliva has a broad range of virus loads (10-100,000 cp/µL) 37 ; 2) saliva contains many heterogeneous components, some of which are inhibitory to most diagnostic assays.…”