Saliva or Nasopharyngeal Swab Specimens for Detection of SARS-CoV-2

Original: NEJM August 28, 2020

Author(s): Wyllie AL, Fournier J, Casanovas-Massana A, et al

Reviewer: Stylianos Loukides, e-Learning Director

Published: 30 Aug, 2020

The emergence and spread of 2019 novel coronavirus disease (COVID-19) and the associated acute respiratory distress syndrome (ARDS) are causing a growing global public health crisis.Rapid and accurate diagnostic tests are essential for controlling the ongoing Covid-19 pandemic.The current standard diagnostic approach is to obtain a nasopharyngeal swab specimen and then to perform a quantitative reverse-transcriptase polymerase chain reaction (RT-qPCR) to detect SARS-CoV-2. Saliva specimens may be an alternative diagnostic sample. Rigorous evaluation is needed to determine how saliva specimens compare with nasopharyngeal swab specimens with respect to sensitivity in detection of SARS-CoV-2 during the course of infection.

The current study wanted to determine whether the traditional nasopharyngeal swab specimen is comparable with the saliva one.

A total of 70 inpatients with Covid-19 participated. After Covid-19 was confirmed with a positive nasopharyngeal swab specimen at hospital admission, the authors obtained additional samples from the patients during hospitalization and they tested saliva specimens collected by the patients themselves and nasopharyngeal swabs collected from the patients at the same time point by health care workers.

The results showed more SARS-CoV-2 RNA copies in the saliva specimens than in the nasopharyngeal swab specimens. In addition, a higher percentage of saliva samples than nasopharyngeal swab samples were positive up to 10 days after the Covid-19 diagnosis. These findings suggest that saliva specimens and nasopharyngeal swab specimens have at least similar sensitivity in the detection of SARS-CoV-2 during the course of hospitalization. Interenstingly, during the clinical course, the authors observed less variation in levels of SARS-CoV-2 RNA in the saliva specimens than in the nasopharyngeal swab specimens.

The study has some practical messages which are mainly attributed to the fact that saliva specimens are more easily obtained and could be collected by patients themselves. Given the growing need for testing, the current findings provide support for the potential of saliva specimens in the diagnosis of SARS-CoV-2 infection.

Respiratory digests
Respiratory infections