SALIVA MAY BE CONSIDERED AS RELIABLE TOOL FOR DIAGNOSIS OF COVID-19 WHEN COMPARED WITH NASOPHARYNX OR THROAT SWABS

Selection Criteria With no date or language restrictions, an electronic search to evaluate the available data regarding the use of saliva as a reliable tool for coronavirus 2019 (COVID-19) diagnosis and monitoring was conducted on July 22, 2020, using the following databases: (1) PubMed, (2) Embase, (3) LILACS, (4) Scopus, and (5) Web of Science, and the references of the related articles were cross-checked. The review included case reports and series, case-control, cross-sectional, and prospective observational studies. Key Study Factor The reliability of saliva as a testing sample for the diagnosis of COVID-19 as compared with gold standard samples (nasopharynx and throat swabs) was evaluated in 28 studies conducted in 10 different countries. A total of 2095 patients were included in this review. The most used SARS-CoV-2 detection test in saliva samples was the RT-qPCR. Drooled saliva, coughed-out saliva, oral swabs, glandular secretion, posterior oropharyngeal saliva, and throat saliva were used as specimens. Main Outcome Measure Sensitivity and specificity of reverse-transcription quantitative polymerase chain reaction (RT-qPCR) using saliva as samples in detecting the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) were investigated. Main Results Twenty-five studies evaluated COVID-19 markers in adults, and three studies assessed the same markers in neonates and pediatric patients. Twenty-eight studies detected the presence of SARS-CoV-2 RNA in saliva. The reported viral load ranged from 9.9 3 102 to 1.2 3 108 copies/ml. Nine studies compared the sensitivity or specificity of RT-qPCRanalyzed saliva specimens with that of the throat and nasopharyngeal swabs, the gold standard for COVID-19 diagnosis. This varied from 66% to 92%, and from 97% to 100%, respectively. One study analyzed the cost of different testing samples and reported US $8.24 per 100 saliva specimens compared with US $104.87 per 100 for nasopharyngeal swabs. Two studies reported impact of the times of saliva collection on the test results. The cycle threshold values of posterior oropharyngeal saliva specimens collected at different time points were obtained and analyzed, differences during the day were identified, as were higher viral loads early in the morning versus bedtime. Saliva specimens collected during the day had a lower rate of positive concordance with the nasopharyngeal swab viral load than saliva collected early in the morning. Conclusions The detection of SARS-CoV-2 in the saliva of patients with COVID-19 has been confirmed, with diagnostic performance comparable with the current standards (nasopharyngeal and throat swabs); however, there is a lack of understanding of salivary biomolecules that could be used for salivary diagnostics in the context of COVID-19 infection.