Saliva as a Noninvasive Specimen for Detection of SARS-CoV-2

Abstract

12Diagnostic testing for COVID-19 is central to controlling the global pandemic. Recently, To and 13 colleagues reported that 20 of 23 (87%) patients who had SARS-CoV-2 detected by reverse-14 transcriptase PCR (RT-PCR) in nasopharyngeal swabs (NPS) or sputum also had SARS-CoV-2 15 detectable in saliva (1). The use of saliva has several advantages compared to collection of NPS. In 16 particular, the close contact involved in swab collection poses a risk to healthcare workers, and 17 collection of saliva may reduce this risk. Further, saliva collection does not require specialised 18 consumables, causes less patient discomfort, and may be a useful sample for self-collection (2). 20We further investigated the feasibility and utility of saliva collection from ambulatory patients 21 presenting to a dedicated COVID-19 screening clinic at the Royal Melbourne Hospital (RMH), 22Melbourne, Australia. Between 25 th March and 1 st April 2020, 622 patients were tested for COVID-23 19 through the screening clinic. All patients had NPS, and 522/622 (83.9%) patients also provided 24 saliva. Patients were asked to pool saliva in their mouth for 1-2 minutes prior to collection, and gently 25 spit 1-2 mL of saliva into a 25mL collection pot. Neat saliva specimens were transported to the 26 laboratory where an approximate 1:1 ratio of liquid Amies media was immediately added. We 27 specifically chose to use liquid Amies media in order to: (i) evaluate the use of an alternative transport 28 media in the face of global shortages of viral transport medium (VTM), and (ii) to preserve VTM in 29 our own laboratory. The median time from sample collection to addition of media was 180 minutes 30 (range 55 -537 minutes). NPS and saliva specimens underwent nucleic acid extraction on the Qiagen 31 EZ1 platform (QIAGEN, Hilden, Germany). An extraction volume of 200uL of the sample was used, 32 with RNA eluted in 60uL. Reverse-transcriptase PCR (RT-PCR) testing was performed using a 33 multiplex RT-PCR test for SARS-CoV-2 and other seasonal coronaviruses (Coronavirus Typing (8-34 well) assay, AusDiagnostics, Mascot, Australia). All positive NPS samples for SARS-CoV-2 35 underwent confirmatory testing at a local reference laboratory (the Victorian Infectious Diseases 36 Reference Laboratory) using previously published primers (3). 38Overall, 39/622 (6.3%; 95% confidence interval [CI] 4.6%-8.5%) patients had PCR-positive NPS, and 39 33/39 patients (84.6%; 95% CI 70.0%-93.1%) had SARS-CoV-2 detected in saliva. The median cycle 40 threshold (Ct) value was significantly lower in NPS than saliva ( Figure 1A), suggestive of higher viral 41 loads in NPS, and in both samples, there was a correlation between Ct value and days from symptom 42 onset ( Figure 1B). To assess specificity, a subset of saliva specimens from 50 patients with PCR-43 negative swabs was also tested. Of note, SARS-CoV-2 was detected in 1/50 (2%; 95% CI 0.1%-44 11.5%) of these saliva samples, which may reflect differing quality of NPS collection. 46To date, studies assessing the utilit...

Saliva is less sensitive than nasopharyngeal swabs for COVID-19 detection in the community setting

“…In this study, only 84.9% of NPS samples were confirmed with saliva. This reduced sensitivity seems to be related to reduced viral titer in saliva samples [12] as well as differences in temporal dynamics in shedding in upper respiratory locations versus saliva [13,14] . Lastly, in convalescent patients, viral titers remain at detectable levels up to 21 days after initial testing [15,16] .…”

Frequency and Duration of SARS-CoV-2 Shedding in Oral Fluid Samples Assessed by a Modified Commercial Rapid Molecular Assay

“…The WHO currently recommends RT-PCR testing using nasopharyngeal (NPS) and oropharyngeal swabs (OPS) as gold standard for SARS-CoV-2 diagnosis and for monitoring viral load [ 4 , 5 ]. OF has been suggested as an alternate clinical sample, easy and safer to collect, minimizing exposure of healthcare workers and could be useful for making a diagnosis and measuring SARS-CoV-2 viral load and viral shedding during the course of the illness and convalescence [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ]. To et al, demonstrated that SARS-CoV-2 was present in OF specimen of 11 out of 12 patients, with viral load being higher during the first week after symptoms onset and declining thereafter, being detectable until 25 days after symptoms onset (DSO) [ 14 , 15 ].…”

Efficacy of a novel SARS-CoV-2 detection kit without RNA extraction and purification

“…Self-collecting saliva specimens are noninvasive tool for the virus detection and reduce a risk of health care workers. A series of recent studies have shown efficacy of saliva as a diagnostic tool(6-10). We recently reported 97% concordance rate between nasopharyngeal swab samples and saliva in the detection of SARS-CoV-2(11).…”