Accuracy and stability of saliva as a sample for reverse transcription PCR detection of SARS-CoV-2.

COVID-19 prevalence has increased worldwide. Reverse transcription (RT)-PCR-based SARS-CoV-2 detection has majorly contributed to COVID-19 diagnosis. Although nasopharyngeal swab samples are commonly used for RT-PCR, infection risk is high among the healthcare personnel during sample collection. Saliva, which can be self-collected by patients even at home, has been proposed as a sample for RT-PCR-based SARS-CoV-2 detection, thus potentially reducing the infection risk among healthcare personnel.1 2 However, few studies have assessed the accuracy of RT-PCR analysis using multiple saliva samples. Furthermore, salivary ribonuclease is speculated to affect the analysis of stored samples.3 From 15 May to 16 July 2020, we obtained nasopharyngeal swabs and saliva samples simultaneously, from patients admitted to Keio University Hospital (Tokyo, Japan) for COVID-19 treatment and from the university staff presenting symptoms suggesting acute viral infections, including fever, upper or lower respiratory symptoms, or diarrhoea. Nasopharyngeal swab samples were collected by trained medical staff using a FLOQ SWAB and a BD UVT container (BD, Franklin Lakes, New Jersey, USA), and saliva samples were collected by patients themselves in sterile containers after 1 min of salivation. Real-time RT-PCR-based SARS-CoV-2 detection was simultaneously performed for both samples, using LightCycler96 (Roche, Basel, Switzerland) using the 2019 Novel Coronavirus Detection Kit (Shimadzu, Kyoto, Japan) in accordance with the manufacturer’s instructions using N1 and N2 primers and probes.4 Ct values of <40 for either primer were considered as a positive result, and the results were compared between the two samples. Furthermore, to assess the stability of saliva samples, samples with …