Viral Load Kinetics of SARS-CoV-2 Infection in Saliva in Korean Patients: a Prospective Multi-center Comparative Study

Abstract

Background: This study was performed to compare the viral load and kinetics of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) in saliva with those in standard nasopharyngeal/oropharyngeal (NP/OP) swabs. Methods: Fifteen patients with SARS-CoV-2 infection from four hospitals were prospectively enrolled and matched samples of nasopharyngeal/oropharyngeal swabs and saliva were collected at Day 1 of admission and every other day till consequently negative for two times. Real-time reverse transcription polymerase chain reaction (rRT-PCR) was performed to detect the envelope (E) and RNA-dependent RNA polymerase (RdRP) genes. Results: The cycle threshold values of saliva were comparable to those of NP/OP swabs overall (P = 0.720, Mann-Whitney U test). However, the overall sensitivity of rRT-PCR using saliva was 64% (34/53), which is lower than the 77% (41/53) using NP/OP swabs. The sensitivity of rRT-PCR using saliva was especially lower in early stage of symptom onset (1-5 days; 8/15; 53%) and in patients who did not have sputum (12/22; 55%). Conclusion: Saliva sample itself is not appropriate for initial diagnosis of coronavirus disease 2019 (COVID-19) to replace NP/OP swabs, especially for the person who does not produce sputum. COVID-19 cannot be excluded when the test using saliva is negative, and it is necessary to retest using NP/OP swabs.

Does sampling saliva increase detection of SARS-CoV-2 by RT-PCR? Comparing saliva with oro-nasopharyngeal swabs

“…Our results also revealed that at the early stages of the infection, saliva sampling had a lower sensitivity to detect viral RNA compared to other sampling methods. Although some recent studies have shown similar results to ours, there are also other studies suggesting that saliva samples are compatible with the results of nasopharyngeal samples starting from the early period of the disease ( Azzi et al, 2020 , To et al, 2020 , Pasomsub et al, 2020 , Kam et al, 2020 ; Chong et al, 2020 , Jamal et al, 2020 ; Kim et al, 2020 ; Kojima et al, 2020 ; Yokota et al, 2020 , Yee et al, 2020 ; Santos et al, 2020 ). Some researchers suggest that saliva sampling can allow for an efficient, relatively inexpensive surveillance system however, they also point to the need for pilot studies ( Fogarty et al, 2020 , Medeiros da Silva et al, 2020 ).…”

Saliva sample for the massive screening of SARS-CoV-2 infection: a systematic review

“…This review included 17 case series, 2 case reports, and 3 massive screenings. Two articles were not peer reviewed 11 , 12 , 20 , 23 – 32 , 30 , 13 , 33 , 34 , 14 , 17 – 22 . Patients.…”

Routine saliva testing for the identification of silent coronavirus disease 2019 (COVID-19) in healthcare workers

“…To determine the case detection percentage with a saliva test, we used recent empirical studies for the estimates of saliva testing sensitivity in the range of 70% -97% [18][19][20] . Since viral load in saliva samples have shown to be comparable to NP samples over time [21][22][23] , we applied this range to the normalized sensitivity curves of NP testing and determined the temporal sensitivity of a saliva test (Appendix: Figure A2). Normalization was done by dividing each point on the fitted NP sensitivity curve by its maximum estimated sensitivity over time.…”