Saliva as a non-invasive specimen for detection of SARS-CoV-2 in adults: a diagnostic validity study

The ideal specimen for the detection of SARS-CoV-2 is unknown. Currently, trained HCWs and specialized collection devices are recommended for the collection of nasopharyngeal (NP) swabs. The collection of such specimens requires close contact between HCWs and patients, which poses a risk of transmission of the virus. Collection of saliva may substantially decrease the risk of transmission of SARS-CoV-2 to HCWs. Other advantages of saliva include that the process of collection is non-invasive and a patient, with education and coaching, could self-collect the specimens. These differences could further reduce the risk to HCWs, decrease PPE usage, and may reduce visits to overburdened health-care facilities. None of the recent studies that investigated the use of saliva (n=6) as a diagnostic tool for COVID-19 [neither recent mid turbinate (MT) studies (n=2)], were designed to detect statistical differences between specimen types or collection methods. It is therefore not clear whether saliva represent a reliable diagnostic specimen and further rigorous research is required. This will be a prospective cross-sectional diagnostic validity study comparing the detection rate and other variables of SARS-CoV-2 in paired saliva, MT and NP specimens in out- patients at Groote Schuur hospital. Knowledge of differences in the mean PCR cycle threshold values of positive paired swabs stratified by symptom duration may guide policy as to when saliva vs. MT vs. NP may be the preferred Covid diagnostic specimen. Therefore, validating saliva for the detection of SARS-CoV-2 infections could prove transformative for patient diagnostics and surveillance.