Evaluation of Saliva as a Matrix for RT-PCR Analysis and Two Rapid Antigen Tests for the Detection of SARS-CoV-2

Abstract

The use of saliva for the detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sparks debate due to presumed lower sensitivity and lack of standardization. Our aim was to evaluate the performance characteristics of (i) saliva collected by the ORAcollectTM device as a matrix for SARS-CoV-2 reverse-transcriptase polymerase chain reaction (RT-PCR), and (ii) 2 saliva rapid antigen tests (AgRDT). From 342 ambulatory individuals, both a nasopharyngeal swab and saliva sample via ORAcollectTM were obtained for a SARS-CoV-2 RT-PCR test. Furthermore, 54 and 123 additionally performed the V-ChekTM or WhistlingTM saliva AgRDT. In total, 35% of individuals screened positive for SARS-CoV-2 via nasopharyngeal swab. Saliva, as a matrix for the RT-PCR, had a specificity of 96.5% and a negative predictive value (NPV) of 91.3%. Interestingly, 6 out of 8 patients thought to be false positive in saliva re-tested positive by nasopharyngeal sampling after 2 to 9 days. Both V-ChekTM and WhistlingTM AgRDT had a lack of sensitivity, resulting in an NPV of 66.9 and 67.3%, respectively. Saliva proved to be a sensitive and specific matrix for SARS-CoV-2 detection by the RT-PCR. In this setting, saliva might have an earlier window of detection than the nasopharyngeal swab. By contrast, both AgRDT showed an unacceptably low sensitivity and NPV.

COVID‐19 rapid antigen tests approved for self‐testing in Australia: published diagnostic test accuracy studies and manufacturer‐supplied information. A systematic review

“…The risk of bias in the participant characteristics domain was low for five studies; 16,17,20‐22 it was high for one study because it included participants known to be SARS‐CoV‐2‐positive, 27 and possibly inappropriate exclusions and inclusions led to concerns about this domain for six studies 18,19,23‐26 . The risk of bias for the index test was low for all but one study, for which concerns were raised by the possibility that participants were not blinded to their RT‐PCR reference test results at the time of the RAT 18 .…”

“…The third Dutch study, in which participants did not have COVID‐19 symptoms, the sensitivity of the Flowflex (27.5%) and the MP Biomedicals nasal self‐tests (20.9%) was similarly low 22 . The fourth study that compared TGA‐approved tests, in a Belgian university hospital outpatient testing clinic, found that the sensitivity of both the V‐Chek (7.7%) and Whistling saliva tests (9.1%), with supervised sample collection, was very low 25 . Sensitivity could not be estimated in the two studies in which no participants were SARS‐CoV‐2‐positive by RT‐PCR 18,19 …”

“…The substantial difference in sensitivity estimates between those supplied by manufacturers (and used to classify tests on the TGA website) and those from independent published studies is concerning. We hope that our findings will increase community awareness of the high risk of false negative results when using RATs for 24 Goodall (2022) 26 Møller (2022) 18 BinaxNow Shah (2021) 23 Landaverde (2022) 27 Roche Zwart (2022) 16 Schuit (2022) 20 Stohr (2022) 17 MP Biomedicals Schuit (2022) 21 (oropharyngeal/nasal) Schuit ( 2022) 21 (nasal) Venekamp (2022) 22 Flowflex Schuit (2022) 21 Venekamp (2022) 22 All Test Schuit (2022) 20 Whistling De Meyer (2022) 25 V-Chek De Meyer (2022) 25 Clungene Iftner (2022) 19…”

At-Home Saliva Sampling in Healthy Adults Using CandyCollect, a Lollipop-Inspired Device

“…It is easily treatable with antibiotics when diagnosed; however, diagnosis can be thwarted by invasive sampling methods which discourage children (and adults) from successfully completing the sampling process and may result in decreased yields . The gold standard method for diagnosing strep throat is a pharyngeal swab coupled with bacterial culture; , however, qPCR has become a new tool that can be implemented in the diagnosis of strep throat, allowing saliva sampling as a means for diagnosis. , Current methods for saliva sampling include spit tubes (e.g., SpeciMAX Stabilized Saliva Collection Kit), drooling (e.g., SalivaBio Saliva Collection Aid), swabs (e.g., Eswab), and cotton rolls (e.g., Salivette, SalivaBio Oral Swab). − In recent years, others have also developed lollipop-inspired devices, such as Self-LolliSponge (with lemon-aromatized cap), and non-conventional sampling devices using absorbing materials, e.g., V-Chek test card and Whistling midstream test. , The CandyCollect device was designed to facilitate easy, non-invasive, at-home sampling of saliva, particularly for children, which is then shipped to a lab for analysis and diagnosis . The device sampling mimics the action of eating a lollipop, featuring a polystyrene stick with an open microfluidic channel for bacterial capture and isomalt candy that functions as a timer to ensure sufficient sampling time.…”

“…9−11 In recent years, others have also developed lollipop-inspired devices, such as Self-LolliSponge (with lemon-aromatized cap), and non-conventional sampling devices using absorbing materials, e.g., V-Chek test card and Whistling midstream test. 12,13 The CandyCollect device was designed to facilitate easy, non-invasive, at-home sampling of saliva, particularly for children, which is then shipped to a lab for analysis and diagnosis. 2 The device sampling mimics the action of eating a lollipop, featuring a polystyrene stick with an open microfluidic channel for bacterial capture and isomalt candy that functions as a timer to ensure sufficient sampling time.…”