Saliva Samples for Detection of SARS-CoV-2 in Mildly Symptomatic and Asymptomatic Patients

Abstract

Background: The ongoing Covid-19 pandemic has been rapidly spreading throughout the world with confirmed case numbers already exceeding 10 millions. Implementation of infection control measures and public health interventions through timely diagnosis of suspected cases seems the most efficient way to control the outbreak.The reference standard for Covid-19 diagnosis is real-time reverse transcriptase polymerase chain reaction (RT-PCR) based SARS-CoV-2 RNA detection in respiratory samples. Although nasopharyngeal swabs are the most commonly utilized samples for diagnosis, collecting these specimens requires healthcare workers, causes discomfort for patients and necessitates the use of personal protective equipment since it presents a nosocomial transmission risk.We aimed to assess the diagnostic value of saliva samples in mildly symptomatic and asymptomatic patients with confirmed Covid-19 disease.Methods: We did a cohort study to validate the use of saliva for SARS-CoV-2 detection in mildly symptomatic and asymptomatic patients with confirmed diagnosis of Covid-19. We obtained self-collected saliva samples from patients within 12 hours after the diagnosis of Covid-19 provided by RT-PCR on nasopharyngeal swabs. Saliva samples of the patients were analyzed by RT-PCR.Findings: In May 2020, 28 asymptomatic and 25 mildly symptomatic patients were enrolled in the study. The median age was 37 years (range 4-70). None of the patients had fever on presentation. Nine (%17) patients had patchy ground-glass opacities on chest tomography.Among 53 patients with SARS-CoV-2 detected in the nasopharyngeal sample, the real-time RT-PCR was positive in the saliva specimens in 48 (90·56%) patients. The mean cycle threshold (CT) values for nasopharyngeal and saliva specimens (27·80±3·44 and 30·64±2·83, respectively) were significantly correlated between the two sample types (p=0·016).The mean CT values of nasopharyngeal and saliva samples in mildly symptomatic and asymptomatic patients (27·18±3·53 and 30·24±3·29 vs. 28·36±3·31 and 30·98±2·39, respectively) were not significantly different (p=0·236 and p=0·733, respectively).The mean CT values for nasopharyngeal and saliva specimens in patients with evidence of pneumonia on tomography were lower than those without pneumonia (26·23±3·56 and 29·15±3·90 vs. 28·12±3·36 and 30·94±2·52, respectively) although the difference was not significant (p=0·077 and p=0·154, respectively).Interpretation: The sensitivity of SARS-CoV-2 detection from saliva is comparable to nasopharyngeal swabs in mildly symptomatic and asymptomatic patients with Covid-19. Saliva specimens can be considered as a reliable and less resource intensive alternative to nasopharyngeal specimens for screening asymptomatic SARS-CoV-2 infections.Funding Statement: This study was supported by donation of qPCR Detection Kit from Bioeksen (Bioeksen R&D, Istanbul, Turkey).Declaration of Interests: The authors declare no competing interests.Ethics Approval Statement: This study was approved by both the Republic of Turkey Ministry of Health COVID-19 Scientific Research Evaluation Commission (Approval date: 02/05/2020; number: 2020-05- 02T16-07-46) and the Local Ethics Committee of Kafkas University Faculty of Medicine (Approval date: 06/05/2020 number: 80576354-050-99/131). The informed consent form had been obtained from each patient before the saliva specimens were collected.