Detection of SARS-CoV-2 RNA using RT-qPCR in nasopharyngeal swab, saliva, lingual, and buccal mucosal swab.

Coronavirus disease 2019 is diagnosed based on the detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA in nasopharyngeal swabs or saliva using real-time quantitative polymerase chain reaction. Nasopharyngeal swabs should be collected by medical professionals wearing full personal protective equipment (PPE), while saliva can be collected by patients themselves without PPE. However, collecting saliva is difficult for people unable to follow instructions, including infants or unconscious patients. Owing to high viscosity, special attention is required for handling saliva samples in laboratories. To solve these problems, we compared lingual and buccal mucosal swabs (oral swabs) with nasopharyngeal swabs and saliva. Among 13 patients who had SARS-CoV-2 positivity in their nasopharyngeal swabs, 8 and 10 had SARS-CoV-2 positivity in saliva (concordance rate 61.5%) and oral swabs (76.9%), respectively. Among 8 patients with SARS-CoV-2 positivity in saliva, SARS-CoV-2 was also detected in oral swabs in 7 patients (87.5%). We could not obtain saliva samples from 4 patients, but we found perfect concordance of SARS-CoV-2 positivity between nasopharyngeal and oral swabs. Therefore, oral swabs can be used for the detection of SARS-CoV-2 RNA.