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Accuracy and stability of saliva as a sample for reverse transcription PCR detection of SARS-CoV-2
  1. Yoshifumi Uwamino1,2,
  2. Mika Nagata3,
  3. Wataru Aoki3,
  4. Yuta Fujimori3,
  5. Terumichi Nakagawa3,
  6. Hiromitsu Yokota3,
  7. Yuko Sakai-Tagawa4,
  8. Kiyoko Iwatsuki-Horimoto4,
  9. Toshiki Shiraki1,
  10. Sho Uchida2,
  11. Shunsuke Uno2,
  12. Hiroki Kabata5,
  13. Shinnosuke Ikemura5,
  14. Hirofumi Kamata5,
  15. Makoto Ishii5,
  16. Koichi Fukunaga5,
  17. Yoshihiro Kawaoka4,6,
  18. Naoki Hasegawa2,
  19. Mitsuru Murata1
  1. 1 Department of Laboratory Medicine, Keio University School of Medicine, Shinjuku-ku, Tokyo, Japan
  2. 2 Department of Infectious Diseases, Keio University School of Medicine, Shinjuku-ku, Tokyo, Japan
  3. 3 Clinical Laboratory, Keio University Hospital, Shinjuku-ku, Tokyo, Japan
  4. 4 Division of Virology, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo, Japan
  5. 5 Division of Pulmonary Medicine, Department of Internal Medicine, Keio University School of Medicine, Shinjuku-ku, Tokyo, Japan
  6. 6 Influenza Research Institute, Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, Wisconsin, USA
  1. Correspondence to Dr Yoshifumi Uwamino, Department of Laboratory Medicine, Keio University School of Medicine, Tokyo 160-8582, Japan; uwamino{at}

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COVID-19 prevalence has increased worldwide. Reverse transcription (RT)-PCR-based SARS-CoV-2 detection has majorly contributed to COVID-19 diagnosis. Although nasopharyngeal swab samples are commonly used for RT-PCR, infection risk is high among the healthcare personnel during sample collection. Saliva, which can be self-collected by patients even at home, has been proposed as a sample for RT-PCR-based SARS-CoV-2 detection, thus potentially reducing the infection risk among healthcare personnel.1 2 However, few studies have assessed the accuracy of RT-PCR analysis using multiple saliva samples. Furthermore, salivary ribonuclease is speculated to affect the analysis of stored samples.3

From 15 May to 16 July 2020, we obtained nasopharyngeal swabs and saliva samples simultaneously, from patients admitted to Keio University Hospital (Tokyo, Japan) for COVID-19 treatment and from the university staff presenting symptoms suggesting acute viral infections, including fever, upper or lower respiratory symptoms, or diarrhoea. Nasopharyngeal swab samples were collected by trained medical staff using a FLOQ SWAB and a BD UVT container (BD, Franklin Lakes, New Jersey, USA), and saliva samples were collected by patients themselves in sterile containers after 1 min of salivation. Real-time RT-PCR-based SARS-CoV-2 detection was simultaneously performed for both samples, using LightCycler96 (Roche, Basel, Switzerland) using the 2019 Novel Coronavirus Detection Kit (Shimadzu, Kyoto, Japan) in accordance with the manufacturer’s instructions using N1 and N2 primers and probes.4 Ct values of <40 for either primer were considered as a positive result, and the results were compared between the two samples.

Furthermore, to assess the stability of saliva samples, samples with …

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  • Handling editor Tahir S Pillay.

  • YU and MN contributed equally.

  • Contributors YU and MN equally contributed to this work. YU conceived, designed the study, analysed and interpreted the data, and wrote the manuscript. MN conceived, designed the study, performed the assays and analysed the data. WA, YF, TN, YS-T and KI-H performed the assays. TS, ShoUc, ShuUn, HirokK, SI and HirofK collected the data, and all authors discussed the data and critically reviewed and revised the manuscript. All authors have given final approval for this version of the manuscript to be published.

  • Funding This study was funded by Keio University Hospital and partly supported by a Research Program on Emerging and Re-emerging Infectious Diseases (JP19fk0108113) from the Japan Agency for Medical Research and Development and by the National Institutes of Allergy and Infectious Diseases-funded Center for Research on Influenza Pathogenesis (Grant HHSN272201400008C).

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Ethics approval This study was approved by Ethics Committee of Keio University School of Medicine (20 200 063 and 20190337).

  • Provenance and peer review Not commissioned; internally peer reviewed.