Abstract and Introduction
Objective: Using a US Food and Drug Administration (FDA) emergency use authorization (EUA) reverse transcription polymerase chain reaction (RT-PCR) method, we examined the analytic performance accuracy of saliva specimens as compared to nasopharyngeal (NP) specimens in symptomatic patients. Correlation between test results and symptoms was also evaluated.
Methods: Over a 5-week period in 2020, 89 matched saliva and nasopharyngeal swabs were collected from individuals exhibiting symptoms consistent with SARS-CoV-2. Specimens were tested with an FDA EUA-approved RT-PCR method, and performance characteristics were compared.
Results: The concordance rate between saliva and nasopharyngeal testing was 93.26%. The mean cycle threshold value of saliva when compared to the NP specimen was 3.56 cycles higher. As compared to NP swab, saliva testing demonstrates acceptable agreement but lower sensitivity.
Conclusion: When compared to a reference method using NP swabs, the use of saliva testing proved to be a reliable method. Self-collected saliva testing for SARS-CoV-2 allows for a viable option when trained staff or collection materials are in short supply.
As part of the management of the COVID-19 pandemic, accurate detection of infected individuals lies at the forefront of health care. The current criterion standard specimen type, nasopharyngeal (NP) swabs, must be collected by health care professionals and later analyzed via reverse transcription polymerase chain reaction (RT-PCR). The lack of sufficient supplies (collection swabs, viral transport medias, collection tubes) and availability of health care professionals to facilitate viral collection poses a persistent challenge in the detection of SARS coronavirus-2 (SARS-CoV-2). Discomfort reported by patients along with possible transmission associated with the NP collection method highlights the importance of pursuing alternative sampling methods for SARS-CoV-2. Self-collected saliva is a noninvasive sample type that may improve detection of SARS-CoV-2 as compared to NP swabs.[1,2]
The consideration of saliva as a sample type centers around differences in sensitivities to NP swabs and the potential of increasing access to COVID-19 diagnostic tests. As new strains of SARS-CoV-2 continue to emerge and spread, the urgent need for efficient collection and testing methods remains pivotal. Utilization of self-collected saliva may diminish the possibility of SARS-CoV-2 transmission as compared to assisted NP swab testing. Other studies note test results from self-collected saliva specimens demonstrate similar analytical performance to NP samples collected by trained health care professionals. In the summer of 2020, the pandemic greatly affected minorities and disenfranchised communities due to preexisting conditions, crowded living spaces, and lack of access to COVID-19 testing. Newer variants of the virus may affect such communities yet again, further highlighting the importance of providing access to reliable testing with readily collectable specimens. Self-collected saliva samples for detection of the virus could potentially increase access to testing, thus reducing the negative effects on underserved communities.
Our study objective was to assess the viability of saliva as a sample type in detection of SARS-CoV-2, as compared to the standard NP swab, using a high-throughput US Food and Drug Administration (FDA) emergency use authorization (EUA) method. We analyzed cycle threshold (Ct) values to discern sensitivity differences between NP swabs and saliva samples to illustrate the potential utility of saliva as a sample type.
Lab Med. 2022;53(6):580-584. © 2022 American Society for Clinical Pathology