Saliva vs Nasal Swab Testing for COVID-19: Which Test Is Safer, Has Faster Results?

A new study recently revealed that genetic testing of saliva specimens had identified the SARS-CoV-2 virus more quickly than nasal swab tests.

As indicated in a EurekAlert! report, according to professor of occupational and environmental health at the Institute for Applied Environmental Health, University of Maryland School of Public Health, College Park, Donald Milton, MD, DrPH, that is essential as people can transfer COVID-19 before knowing that they have it. He added, earlier detection can lessen the spread of the disease.

The study was motivated by the problem that early in this pandemic, an urgent need to enhance testing was accompanied by scarcity in supplies, especially nasal swabs, which were then the standard method of collecting specimens for testing.

To determine people who have COVID-19, the study authors started performing weekly tests of saliva specimens from healthy community volunteers in 2020 and continued over the next couple of years.

Of the asymptomatic volunteers who tested positive, Milton and his colleagues discovered that the patients would typically exhibit symptoms one to two days after. He said the results made the wonder if saliva was better for catching pre-symptomatic patients than traditional nasal swabs.

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(Photo: KENZO TRIBOUILLARD/AFP via Getty Images)
Fabrice Bureau, vice-rector for Research at the University of Liege, shows how to collect one's saliva for tests to detect Covid-19 at the University of Liege.

Saliva and Nasal Swab Samples Collected

To answer the question, the study investigators used data from companion research of close contacts of those who have confirmed cases of COVID-19.

In the research published in Microbiology Spectrum, the researchers collected saliva and mid-turbinate or nasal swab samples from contacts every two or three days during the volunteers' quarantine period.

Milton explained that all specimens were examined using real-time reverse transcription-polymerase chain reaction or RT-PCR to detect SARS-CoV-2 and gauge the amount of viral RNA in the specimens. They then analyzed how such results changed in the days before, and following the onset of the symptoms.

Public Acceptance of COVID-19 Testing

The professor also explained that, early in the infection, saliva was substantially more sensitive than the mid-turbinate nasal swabs, remarkably so before the start of symptoms.

The study also noted that previous research had shown that pre-symptomatic transmission plays a greater role than the symptomatic spread of the COVID-19 virus.

The findings have implications for improving public acceptance of testing for COVID-19, lessening the cost of mass screening for COVID-19, and improving the safety of healthcare workers who carry out testing, a related SciTechDaily report said.

In the latter-mentioned case, saliva self-testing avoids the close contact between the healthcare worker and the patient that nasal swabbing entails and avoids leading the patients to sneeze and cough, therefore, transmitting virus particles as an outcome of swabbing the sensitive nasal passages, not to mention discomfort to patients.

According to Milton, their study backs the use of saliva in large-scale screening in schools and workplaces to enhance screening rates and early detection of the virus.

He added, they are expecting if quick saliva tests become available, they could be a "major advance from the present nasal swab-based rapid tests."

Report about the COVID-19 saliva testing is shown on Health News's YouTube video below:

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