Validation of self-collected buccal swab and saliva as a diagnostic tool for COVID-19

Abstract

Background: Effective management of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) requires large-scale testing. Collection of nasopharyngeal swab (NPS) by healthcare workers (HCW) is currently used to diagnose SARS-CoV-2, which increases the risk of transmission to HCWs. Self-administered saliva and buccal swabs are convenient, painless and safe alternative sample collection methods. Methods: A cross-sectional single centre study was conducted on 42 participants who were tested positive for SARS-CoV-2 via NPS within the past 7 days. A self-collected saliva and buccal swab and a HCW-collected NPS were obtained. Real-time polymerase chain reaction (RT-PCR) was performed and cycle threshold (CT) values were obtained. Positive percent agreement (PPA), negative percent agreement (NPA) and overall agreement (OA) were calculated for saliva and buccal swabs, as compared with NPS. Results: Among the 42 participants, 73.8% (31/42) tested positive via any one of the 3 tests. With reference to NPS, the saliva test had PPA 66.7%, NPA 91.7% and OA 69.0%. The buccal swab had PPA 56.7%, NPA 100% and OA 73.8%. Presence of symptoms improved diagnostic accuracy. There was no statistically significant association between CT values and duration of symptom onset within the first 12 days of symptoms for all three modalities. Conclusion: Self-collected saliva tests and buccal swabs have only moderate agreement with HCW-collected NPS swabs. Primary screening for SARS-CoV-2 may be performed with a saliva test or buccal swab, with a negative test warranting a confirmatory NPS to avoid false negatives. This combined strategy minimizes discomfort and reduces the risk of spread to the community and HCWs.

COVID-19 diagnosis by RT-qPCR in alternative specimens

“…The second study included 42 individual who tested positive for SARS-CoV-2 by NP swab RT-qPCR within seven days prior to self-collected buccal swab (both cheeks, above and below the tongue, both gums, and on the hard palate), and a positive agreement of 56.7% was observed. (13) Herein we tested gingival fluid as a specimen for SARS-CoV-2 detection by RT-qPCR, and we found a poor concordance rate (15.38%) among RT-qPCR positive samples from NP swabs. Although our data is in agreement with previous data, our concordance rate among positive results was lower than the those reported by Ku et al (14) and Kam et al (12) .…”

ESCMID COVID-19 guidelines: diagnostic testing for SARS-CoV-2

“… In patients with signs and symptoms compatible with severe or critical COVID-19 for the diagnosis of COVID-19 infection, we suggest the use of NAAT in nasopharyngeal swab samples versus NAAT in saliva samples for diagnosis of COVID-19. Weak against Very low [ 13 , 92 , [98] , [99] , [100] , [101] , [102] , [103] , [104] , [105] , [106] , [107] , [108] , [109] , [110] , [111] , [112] , [113] , [114] , [115] , [116] ] 22 In patients with signs and symptoms compatible with COVID-19 of equal or less than 7 days onset , should saliva sampling be used, compared with nasopharyngeal swab sampling for diagnosis of COVID-19 with NAAT? In patients with signs and symptoms compatible with COVID-19 of equal or less than 7 days-onset, we suggest the use of NAAT in saliva samples versus NAAT in nasopharyngeal swab samples for diagnosis of COVID-19.…”

Quantitative SARS-CoV-2 Viral-Load Curves in Paired Saliva Samples and Nasal Swabs Inform Appropriate Respiratory Sampling Site and Analytical Test Sensitivity Required for Earliest Viral Detection

“…Sample types such as anterior-nares or mid-turbinate nasal swabs [20][21][22][23] and saliva [24][25][26][27] To understand the required test sensitivity and the optimal sample type for earliest SARS-CoV-2 detection, we designed a case-ascertained study of household transmission with high-frequency sampling of both saliva and anterior-nares nasal swabs. Building on our earlier work, 14 we enrolled individuals ages 6 years and older who had recently tested positive (household index case), and their exposed household contacts at risk of infection.…”