Salivary diagnostics for COVID-19 prove as reliable as nasopharyngeal swab in new study

Figure 1: Saliva test for COVID-19 — **Figure 1:** Saliva test for COVID-19

Nasopharyngeal swabs administered by health-care workers have become the gold standard in testing for COVID-19. Nasopharyngeal swabs utilize a polymerase chain reaction (PCR)-based platform and demonstrate a high sensitivity and specificity. False negatives and positives can occur, however, and these tests are open to operator error, lab contamination, and handling errors than can further compromise accuracy. The tests can be difficult to take as the swab has to be placed deep into the nasopharyngeal region of the patient, often eliciting an unpleasant sensation. In addition, due to high demand, the process may take up to three weeks to receive laboratory results after administering the test.

A new noninvasive COVID-19 test utilizing salivary diagnostics has recently been released for public and point-of-care use. Sample collection is very easy, and the test is less prone to operator error. The question is, are salivary diagnostics as reliable as the gold standard nasopharyngeal swabs? A new prospective study in the Journal of Clinical Microbiology looked to answer that question.¹

Figure 2: Patient expectorates into a collection tube up to a required volume — **Figure 2:** Patient expectorates into a collection tube up to a required volume

The study, performed at the University of Utah, analyzed more than 1,100 samples from 386 patients, comparing traditional deep nasopharyngeal swabs collected by health-care workers to self-collected samples (by patients) using anterior nasal swabs and saliva collection. Researchers found that patient-collected saliva tests for SARS-CoV-2 was just as accurate as traditional nasopharyngeal swab collection by health-care workers. There was a positive percent agreement of 95% and a negative percent agreement of 98% between the two tests. The study also found that patient-collected anterior nasal swabs were not as accurate as traditional nasopharyngeal swabs, and further refinement of these tests is needed.

Saliva tests (figure 1) have definite benefits over traditional nasopharyngeal swabs:

Health-care workers do not need to be exposed to patients upon collection.
These tests are noninvasive and simple to use.
The patient does not have to go to a clinic with sick patients to be tested.
Lab results can take 48–72 hours depending on demand.

Figure 3: Patient screws on a buffer solution and mixes the saliva and buffer — **Figure 3:** Patient screws on a buffer solution and mixes the saliva and buffer

The salivary diagnostics testing procedure:

The patient expectorates (spits) into a collection tube (figure 2) up to a required volume.
The patient screws on a buffer solution and mixes the saliva and buffer (figure 3).
The patient places the sample in an envelope and mails it overnight to the lab (figure 4).

Mass implementation of a COVID-19 test that is accurate, easy to use, and efficient with test results can assist both health care and public health officials in ending the COVID-19 pandemic in an expedited manner.

Figure 4: Patient places saliva sample in an envelope and mails overnight to lab — **Figure 4:** Patient places saliva sample in an envelope and mails overnight to lab

Editor’s note: All photos are courtesy of the author.

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Editor’s note: This article originally appeared in Perio-Implant Advisory, a newsletter for dentists and hygienists that focuses on periodontal- and implant-related issues. Perio-Implant Advisory is part of the Dental Economics and DentistryIQ network. To read more articles, visit perioimplantadvisory.com and subscribe at this link.

Reference

Hanson KE, Barker AP, Hillyard DR, et al. Self-collected anterior nasal and saliva specimens versus healthcare worker-collected nasopharyngeal swabs for the molecular detection of SARS-CoV-2. J Clin Microbiol. 2020;JCM.01824-20. Published online: August 12, 2020. doi:10.1128/JCM.01824-20

Scott Froum, DDS, a graduate of the State University of New York, Stony Brook School of Dental Medicine, is a periodontist in private practice at 1110 2nd Avenue, Suite 305, New York City, New York. He is the editorial director of Perio-Implant Advisory and serves on the editorial advisory board of Dental Economics. Dr. Froum, a diplomate of the American Board of Periodontology, is a clinical associate professor at SUNY Stony Brook School of Dental Medicine in the Department of Periodontology. He serves on the board of editorial consultants for the Academy of Osseointegration's Academy News. Contact him through his website at drscottfroum.comor (212) 751-8530.

Salivary diagnostics for COVID-19 prove as reliable as nasopharyngeal swab in new study

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