Alliance for Pandemic Preparedness

February 12, 2020

Laboratory diagnosis and monitoring the viral shedding of 2019-nCoV infections



  • The diagnostic accuracy of different respiratory specimens for 2019-nCoV detection is assessed by Yang, et al
  • Specimens were collected from confirmed novel coronavirus pneumonia (NCP; severe or mild) patients in a Guangdong, China hospital; and tested using the Qiagen QIAamp RNA Viral Kit and a Chinese Food & Drug Administration-approved, quantitative RT-PCR 2019-nCoV detection kit. 
  • 866 specimens from 213 hospitalized patients were tested, including nasal swabs (n=490), throat swabs (n=205), sputum (n=142) and bronchoalveolar lavage fluid (BALF; n=29). Sample collection was grouped by days after symptom onset (0-7 days, 8-14 days, and >14 days). 
  • Overall, sputum was found to be the most accurate specimen type for laboratory diagnosis of NCP
    • Sputum specimens taken with 14 days after onset were positive in 74-89% of cases (mild and severe). From 15 days onward, 43-61% continued to test positive. 
    • Nasal swab specimens taken within 14 days after onset were positive in 54-73% of cases, dropping to 50-55% after 14 days.
    • Throat specimens taken within 7 days were positive in 60-61% of cases. From 8 days onward, this dropped to 37%-50% of severe cases and 11%-30% of mild cases.
  • Among 10 severe cases, positive BALF specimens were found from 6-23 days after onset; and 100% tested BALF-positive at 8-14 days after symptom onset. Three mild cases were BALF-negative.
  • Among 13 NCP cases with specimens from upper (throat, nasal, sputum) and lower respiratory (BALF) samples across multiple time periods, viral RNA was reliably detected in the lower respiratory tract of cases of severe NCP cases, but not in upper respiratory samples. 

Yang Y, et al (Feb 12, 2020) Laboratory diagnosis and monitoring the viral shedding of 2019-nCoV infections. Pre-print. Accessed Feb 12 from