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Comparative Study
. 2021 Jan;27(1):126-129.
doi: 10.1016/j.jiac.2020.09.027. Epub 2020 Sep 30.

Comparative evaluation of nasopharyngeal swab and saliva specimens for the molecular detection of SARS-CoV-2 RNA in Japanese patients with COVID-19

Affiliations
Comparative Study

Comparative evaluation of nasopharyngeal swab and saliva specimens for the molecular detection of SARS-CoV-2 RNA in Japanese patients with COVID-19

Daisuke Sakanashi et al. J Infect Chemother. 2021 Jan.

Abstract

Considering the issues of shortage of medical resources and the invasiveness and infection risk involved in the collection of nasopharyngeal swab specimens, there is a need for an effective alternative test specimen for SARS-CoV-2 RNA detection. Here, we investigated suitability of saliva as a non-invasively obtained specimen for molecular detection of SARS-CoV-2 RNA in Japanese patients with COVID-19. In total, 28 paired clinical specimens of saliva and nasopharyngeal swabs were collected from 12 patients at various time points after symptom onset. Each specimen was assayed using reverse transcription real-time polymerase chain reaction (rRT-PCR) on the BD MAX open system using primers and probes targeting the N-gene. The saliva and nasopharyngeal swab specimens showed 19 and 15 positive results, respectively. No invalid (PCR inhibition) result was observed for any specimen. The qualitative results of each specimen obtained in the period immediately after symptom onset were similar. Three convalescent patients presented saliva-positive results, whereas their nasopharyngeal swabs were negative at four different time points, suggesting that saliva may be superior to nasopharyngeal swabs in terms of obtaining stable assay result of SARS-CoV-2. In conclusion, our results suggest that saliva can potentially serve as an alternative to nasopharyngeal swabs as a specimen for SARS-CoV-2 rRT-PCR. As saliva can be collected by patients themselves, it may be an effective way to overcome the shortage of personal protective equipment and specimen sampling tools.

Keywords: Nasopharyngeal swab; Reverse transcription real-time PCR; SARS-CoV-2; Saliva.

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Conflict of interest statement

Declaration of competing interest H. Mikamo has received grant support from Asahi Kasei Pharma Corporation, Shionogi & Co. Ltd., Daiichi Sankyo Co., Ltd., Sumitomo Dainippon Pharma Co., Ltd., Pfizer Japan Inc. and FUJIFILM Toyama Chemical Co., Ltd., payment for lectures from Astellas Pharma Inc., MSD K.K., Daiichi Sankyo Co., Ltd., Sumitomo Dainippon Pharma Co., Ltd., MIYARISAN Pharmaceutical Co., Ltd. Becton, Dickinson and Company Japan, and FUJIFILM Toyama Chemical Co. Ltd. The other authors declare that they have no conflicts of interest.

Figures

Fig. 1
Fig. 1
Comparison between SARS-CoV-2 detection from nasopharyngeal swab and saliva specimens using reverse transcription real-time polymerase chain reaction (rRT-PCR) at various time points after symptom onset in seven cases of COVID-19. “+” and “-” indicate “positive” and “negative”, respectively. Frames around indicates the difference in results between nasopharyngeal swab and saliva.
Fig. 2
Fig. 2
Comparison between threshold cycle values from nasopharyngeal swab and saliva specimens in SARS-CoV-2 reverse transcription real-time polymerase chain reaction (rRT-PCR) at various time points after symptom onset in seven cases of COVID-19. Small scale of diagram indicates that only nasopharyngeal swab was assayed.

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