Evaluation of Self-collected Saliva Samples Without Viral Transport Media for SARS-CoV-2 Testing via RT-PCR and Comparison of Amplicon Sequences Against Commonly Used Primers in Diagnostic Assays.

Introduction: Mass screening for SARS-CoV-2 using nasopharyngeal swabs (NPS) is costly, uncomfortable for patients, and increases the chance of virus exposure to health care workers. Therefore, this study focused on determining if self-collected unpreserved saliva can be an effective alternative to NPS collection in COVID-19 surveillance.
Materials and Methods: In this study, patients being tested for SARS-CoV-2 using NPS were asked to provide a saliva sample to compare their results. NPS samples were evaluated for SARS-CoV-2 using BioFire® FilmArray® Torch® or Cepheid® GeneXpert® systems while saliva samples were evaluated using an in-house developed reverse transcriptase polymerase chain reaction (RT-PCR) which targeted the Envelope (E) and Nucleocapsid (N) genes.
Results: Detection of SARS-CoV-2 using self-collected saliva was found to be only slightly less accurate (<5%) than testing using NPS. In addition, initial saliva RT-PCR identified 27 positive subjects, 18 of which provided amplicons sufficient for confirmatory sequencing. The sequencing data showed a genetic shift in the virus within our population sometime between 22 June and July 8, 2021 from Alpha to Delta variant.
Conclusions: The saliva sample collection method identifies the E gene in SARS COVID-2 samples which provides an alternative specimen source to the NPS. This identifies the S gene and ORF1ab. Saliva collection is more convenient to the patient, yields comparable results to NPS collection, and potentially increases Covid-19 surveillance.
(Published by Oxford University Press on behalf of the Association of Military Surgeons of the United States 2024. This work is written by (a) US Government employee(s) and is in the public domain in the US.)