Saliva as a Diagnostic Specimen for SARS-CoV-2 by a PCR-Based Assay: A Diagnostic Validity Study

Background: An outbreak of a novel coronavirus (SARS-CoV-2) that began in Wuhan, has spread rapidly to more than 26 countries. False negative diagnosis of respiratory samples, predominantly nasal or throat swabs, has made diagnoses and control difficult. Methods: To identify the detection rates in different respiratory sample types, we recruited 65 patients with confirmed SARS-CoV-2 infection and sequentially collected throat swabs, nasal swabs and saliva or sputum, followed by a comparative analysis of quantitative RT-PCR and viral loads. Results: The median age of COVID-19 patients recruited for the study was 52.5 years (IQR 39.3-61). Fever (83.3%), cough (54.2%) and expectoration (25.0%) were the most common clinical manifestations. The detection rates of sputum (95.65%, 22/23) and saliva (88.09%, 37/42) were significantly higher than in throat swabs (41.54%, 27/65) and nasal swabs (72.31%, 47/65) ( P <0.001). Further, the Ct Value from sputum, saliva and nasal swabs were significantly higher than in throat swabs, whereas no significant difference was observed between sputum and saliva samples. Conclusions: The detection rate of SARS-CoV-2 is higher in saliva than other respiratory samples. Our results show that saliva and sputum are reliable sample types that can be used to detect SARS-CoV-2, and worthy of clinical promotion. The convenience in sampling saliva may also significantly reduce the risk of infection of medical staff. Funding Statement: This work was supported by the China National Mega-Projects for Infectious Diseases (grant number 2017ZX10103008 and 2018ZX10101001); and the National Natural Science Foundation of China (grant numbers 81672014 and 81702079). Declaration of Interests: All authors had no reported conflicts. Ethics Approval Statement: This study conformed to the ethical guidelines of the 1975 Declaration of Helsinki and was approved by the Institutional Review Board of the First Affiliated Hospital of Zhejiang University.