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Time variation in the probability of failing to detect a case of polymerase chain reaction testing for SARS-CoV-2 as estimated from a viral dynamics model.

  • Ejima, Keisuke1
  • Kim, Kwang Su2
  • Iwanami, Shoya2
  • Fujita, Yasuhisa2
  • Li, Ming1
  • Zoh, Roger S1
  • Aihara, Kazuyuki3
  • Miyazaki, Taiga4
  • Wakita, Takaji5
  • Iwami, Shingo2, 6, 7, 8, 9
  • 1 Department of Epidemiology and Biostatistics, Indiana University School of Public Health-Bloomington, Bloomington, IN 47405, USA. , (India)
  • 2 Department of Biology, Faculty of Sciences, Kyushu University, 744 Motooka Nishi-ku, Fukuoka 819-0395, Japan. , (Japan)
  • 3 International Research Center for Neurointelligence, The University of Tokyo Institutes for Advanced Study, The University of Tokyo, Tokyo, Japan. , (Japan)
  • 4 Department of Infectious Diseases, Nagasaki University Graduate School of Biomedical Sciences, Nagasaki, Japan. , (Japan)
  • 5 Department of Virology II, National Institute of Infectious Diseases, Tokyo, Japan. , (Japan)
  • 6 MIRAI, JST, Saitama, Japan. , (Japan)
  • 7 Institute for the Advanced Study of Human Biology (ASHBi), Kyoto University, Kyoto, Japan. , (Japan)
  • 8 NEXT-Ganken Program, Japanese Foundation for Cancer Research (JFCR), Tokyo, Japan. , (Japan)
  • 9 Science Groove Inc., Fukuoka, Japan. , (Japan)
Published Article
Journal of The Royal Society Interface
The Royal Society
Publication Date
Apr 01, 2021
DOI: 10.1098/rsif.2020.0947
PMID: 33878277


Viral tests including polymerase chain reaction (PCR) tests are recommended to diagnose COVID-19 infection during the acute phase of infection. A test should have high sensitivity; however, the sensitivity of the PCR test is highly influenced by viral load, which changes over time. Because it is difficult to collect data before the onset of symptoms, the current literature on the sensitivity of the PCR test before symptom onset is limited. In this study, we used a viral dynamics model to track the probability of failing to detect a case of PCR testing over time, including the presymptomatic period. The model was parametrized by using longitudinal viral load data collected from 30 hospitalized patients. The probability of failing to detect a case decreased toward symptom onset, and the lowest probability was observed 2 days after symptom onset and increased afterwards. The probability on the day of symptom onset was 1.0% (95% CI: 0.5 to 1.9) and that 2 days before symptom onset was 60.2% (95% CI: 57.1 to 63.2). Our study suggests that the diagnosis of COVID-19 by PCR testing should be done carefully, especially when the test is performed before or way after symptom onset. Further study is needed of patient groups with potentially different viral dynamics, such as asymptomatic cases.

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