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Reliability of induced sputum test is greater than that of throat swab test for detecting SARS-CoV-2 in patients with COVID-19: A multi-center cross-sectional study

  • Lai, Tianwen1
  • Xiang, Fangfei2
  • Zeng, Jianfeng3
  • Huang, Yingzi4
  • Jia, Liping5
  • Chen, Hui6
  • Wu, Jiayuan1
  • Xie, Jianfeng4
  • Liu, Shuna1
  • Deng, Wei1
  • Zheng, Weiqiang1
  • Huang, Yang1
  • Zhang, Qinfu1
  • Luo, Qingfeng1
  • Mo, Fan1
  • Long, Lieming1
  • Zhang, Wuying1
  • Chen, Wenna1
  • Han, Huanqin1
  • 1 Affiliated Hospital of Guangdong Medical University, China , (China)
  • 2 Guangzhou Medical University, China , (China)
  • 3 The Third People’s Hospital of Shenzhen, China , (China)
  • 4 Southeast University, China , (China)
  • 5 Huanggang Central Hospital, China , (China)
  • 6 The First Affiliated Hospital of Soochow University, China , (China)
Published Article
Landes Bioscience
Publication Date
Oct 19, 2020
DOI: 10.1080/21505594.2020.1831342
PMID: 33073676
PMCID: PMC7575004
PubMed Central


We previously reported that sputum induction was more sensitive than throat swabs for the detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in two convalescent coronavirus disease 2019 (COVID-19) patients; however, the value and safety of induced sputum testing require further study. We conducted a prospective multi-center cross-sectional study to compare induced sputum to throat swabs for SARS-CoV-2 detection. Confirmed COVID-19 patients from six hospitals in six cities across China who received one or more negative RT-PCR result for SARS-CoV-2 were enrolled, and paired specimens (induced sputum and throat swabs; 56 cases) were assayed. In three paired samples, both the induced sputum and throat swabs were positive for SARS-CoV-2. The positive rate for induced sputum was significantly higher than for throat swabs both overall (28.6% vs 5.4%, respectively; p < 0.01). Patients were divided according to time span from onset of illness to sample collection into the more-than-30-day (n = 26) and less-than-30-day (n = 30) groups. The positive rate for induced sputum was also significantly higher than for throat swabs in the less-than-30-day group (53.3% vs 10.0%, respectively; p < 0.001). For the more-than-30-day group, all paired samples were negative for SARS-CoV-2. Blood oxygen saturation, respiratory rate, and heart rate remained stable during sputum induction and no staff were infected. Because induced sputum is more reliable and has a lower false-negative rate than throat swabs, we believe induced sputum is more useful for the confirmation of COVID-19 and is safer as a criterion for release from quarantine.

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