Change in saliva RT-PCR sensitivity over the course of SARS-CoV-2 infection

JAMACongrave-Wilson Z, Lee Y, Jumarang J, et al. | September 23, 2021


A prospective, longitudinal study was conducted to determine the testing time frame that may aid in optimizing sensitivity of saliva-based SARS-CoV-2 molecular testing for SARS-CoV-2 detection.

  • Recruited were individuals exposed to a household member with RT-PCR–confirmed SARS-CoV-2 within 2 weeks.

  • Every 3 to 7 days, collection of paired nasopharyngeal and saliva samples was done for up to 4 weeks or until 2 negative nasopharyngeal test results.

  • RT-PCR for SARS-CoV-2 N1 and N2 genes was performed; a positive result was defined as cycle threshold less than 40.

  • From 404 participants, a total of 889 paired nasopharyngeal swab-saliva samples were obtained.

  • Detection of SARS-CoV-2 was observed in 524 nasopharyngeal (58.9%) and 318 saliva (35.7%) specimens.

  • In 258 pairs (29.0%), both specimens had detection of SARS-CoV-2.

  • Saliva from symptomatic individuals was identified as sensitive for detecting SARS-CoV-2 during initial weeks of infection, but sensitivity was less than 60% at all time points in asymptomatic SARS-CoV-2 carriers.

  • Researchers recommend considering low saliva sensitivity in asymptomatic infections, as optimization of COVID-19 testing strategies takes place in workplaces, schools, and other shared spaces.

  • For asymptomatic COVID-19 screening, use of saliva-based RT-PCR is not supported.

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