[Open Forum Infectious Diseases] Early-Morning vs Spot Posterior Oropharyngeal Saliva for Diagnosis of SARS-CoV-2 Infection: Implication of Timing of Specimen Collection for Community-Wide Screening

Open Forum Infectious Diseases, 7 June 2020

Derek Ling-Lung Hung, Xin Li, Kelvin Hei-Yeung Chiu, Cyril Chik-Yan Yip, Kelvin Kai-Wang To, Jasper Fuk-Woo Chan, Siddharth Sridhar, Tom Wai-Hin Chung, Kwok-Cheung Lung, Raymond Wai- To Liu, Grace Sze-Wai Kwan, Ivan Fan-Ngai Hung, Vincent Chi-Chung Cheng, Kwok-Yung Yuen


  • Posterior oropharyngeal saliva was collected at 5 different time points within the same day from 18 patients with previously confirmed SARS-CoV-2 infection by molecular testing.
  • Eight out of 13 subjects had a higher viral load in the early morning than the rest of the 4 time points (before lunch, before teatime at 3 PM, before dinner, before bedtime).
  • The result suggests a diurnal variation of viral shedding from the upper respiratory tract with a trend showing higher viral load in the early morning.
  • For community screening purposes, posterior oropharyngeal saliva could be taken throughout the day, but preferably in the early morning to maximize the yield.

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