J Korean Med Sci.  2020 Aug;35(31):e287. 10.3346/jkms.2020.35.e287.

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

Affiliations
  • 1Department of Infectious Diseases, Chonnam National University Hospital, Gwangju, Korea
  • 2Department of Infectious Diseases, Keimyung University Dongsan Hospital, Daegu, Korea
  • 3Department of Infectious Diseases, Chonnam National University Bitgoeul Hospital, Gwangju, Korea
  • 4Department of Infectious Diseases, Chonnam National University Hwasun Hospital, Hwasun, Korea
  • 5Department of Laboratory Medicine, Chonnam National University Hospital, Gwangju, Korea

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.

Keyword

SARS-CoV-2 PCR; Saliva; Nasopharyngeal Swab; Oropharyngeal Swab
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