Challenges in use of saliva for detection of SARS CoV-2 RNA in symptomatic outpatients
Marie L Landry, Jody Criscuolo, David R Peaper, Marie L Landry, Jody Criscuolo, David R Peaper
Abstract
Background: A major expansion in SARS CoV-2 testing is urgently needed. Saliva is an attractive option as an alternative for nasopharyngeal swabs (NPS), since saliva can be self-collected, is non-invasive, and sample quality is not dependent on the expertise of the collector.
Objective: To compare SARS CoV-2 positivity on paired NPS and saliva samples.
Study design: NPS and paired saliva samples were prospectively collected from symptomatic outpatients suspected of having COVID-19 and were tested by real-time RT-PCR.
Results: In total, 35/124 (26.6 %) samples were RT-PCR positive, with 33/35 positive by NPS (sensitivity = 94.3 % (95 % CI 81.4%-99.0%)) and 30/35 by pure saliva (sensitivity = 85.7 % (95 % CI 70.6%-93.7%)), for an overall agreement of 117/124 (94.4 %). The median cycle threshold value was significantly lower for NPS than for saliva (p = 0.0331). A third or more of pure saliva samples from symptomatic patients were thick, stringy, and difficult to pipet.
Conclusions: Real-time RT-PCR of pure saliva had an overall sensitivity for SARS CoV-2 RNA detection of 85.7 % when compared to simultaneously collected NPS. Our study highlighted the need to optimize collection and processing before saliva can be used for high volume testing.
Keywords: COVID-19; Nasopharyngeal swab; Real-time RT-PCR; SARS CoV-2; Saliva.
Conflict of interest statement
The authors have no conflicts to declare.
Copyright © 2020 Elsevier B.V. All rights reserved.
Figures
References
- Hanson K.E., Caliendo A.M., Arias C.A. Infectious diseases society of America guidelines on the diagnosis of COVID-19 [published online ahead of print, 2020 Jun 16] Clin. Infect. Dis. 2020 doi: 10.1093/cid/ciaa760. ciaa760.
- Williams E., Bond K., Zhang B., Putland M., Williamson D.A. Saliva as a non-invasive specimen for detection of SARS-CoV-2 [published online ahead of print, 2020 Apr 21] J. Clin. Microbiol. 2020 doi: 10.1128/JCM.00776-20. JCM.00776-20.
- Azzi L., Carcano G., Gianfagna F. Saliva is a reliable tool to detect SARS-CoV-2. J. Infect. 2020;81(1):e45–e50. doi: 10.1016/j.jinf.2020.04.005.
- Azzi L., Carcano G., Dalla Gasperina D., Sessa F., Maurino V., Baj A. Two cases of COVID-19 with positive salivary and negative pharyngeal or respiratory swabs at hospital discharge: a rising concern [published online ahead of print, 2020 Apr 25] Oral Dis. 2020 doi: 10.1111/odi.13368.
- To K.K., Tsang O.T., Leung W.S., Tam A.R., Wu T.C., Lung D.C. Temporal profiles of viral load in posterior oropharyngeal saliva samples and serum antibody responses during infection by SARS-CoV-2: an observational cohort study. Lancet Infect. Dis. 2020;20:565–574.
- Wyllie A.L., Fournier J., Casanovas-Massana A., Campbell M., Tokuyama M., Vijayakumar P. Saliva is more sensitive for SARS-CoV-2 detection in COVID-19 patients than nasopharyngeal swabs. medRxiv. 2020;(April (22)) doi: 10.1101/2020.04.16.20067835.
- McCormick-Baw C., Morgan K., Gaffney D. Saliva as an alternate specimen source for detection of SARS-CoV-2 in symptomatic patients using Cepheid Xpert Xpress SARS-CoV-2 [published online ahead of print, 2020 May 15] J. Clin. Microbiol. 2020 doi: 10.1128/JCM.01109-20. JCM.01109-01120.
Source: PubMed