Coming soon: Use of saliva for Covid-19 testing

Kenya Morans basketball team official testing for COVID-19 during the unveiling of the team at Nyayo National Stadium. November 7, 2020. [Jonah Onyango, Standard]

The first picture that probably comes to mind when you hear of a coronavirus test is a special 6-inch cotton swab being inserted in your nostrils or throat through your mouth.

Though painless, the process is especially uncomfortable and the medic needs at least 15 seconds to scan through each nostril opening before they are satisfied that they have enough sample for testing. This is called a viral test.

While the swab test tells only if one has the virus in the body at the moment, blood samples have been used to determine whether you have ever been infected with coronavirus and had no symptoms showing. This is called an antibody test. It helps researchers know how widespread the disease is in a specific area.

Enter the saliva-based antibody test

A recent test has now been found to accurately detect the presence of SARS-CoV-2 from small samples of saliva. This test, if approved by the FDA, could be an alternative to blood-sample antibody tests for research and clinical use.

Developed by scientists at Johns Hopkins Bloomberg School of Public Health, the noninvasive test will possibly make it easier to identify people that have been infected at a population level.

Saliva samples can be collected by rubbing a sponge between people’s teeth and gums, where saliva is known to be particularly enriched with antibodies. In other saliva tests, people collect their own samples by spitting into a small pot. 

Is it accurate?

Small studies have so far hinted that saliva testing is as sensitive as nasopharyngeal (NP) swab tests in high risk populations. While NP swab samples are considered the gold standard in generating accurate results, different studies done by researchers from Yale and Canada have suggested that saliva analysis is not overly less sensitive than swab analysis and might even yield less variable results.

For instance, among 70 patients admitted to Yale-New Haven Hospital suspected to have Covid-19, saliva samples often contained more copies of SARS-CoV-2 than swab samples did. A higher percentage of saliva samples also turned positive up to 10 days after the initial diagnosis.

Experiments have generally suggested that people who are infected with the virus develop detectable antibodies in saliva at roughly the same time as they do in blood, about 10 days after symptoms start.

Saliva tests trials are already in trial in different parts of the world. Last week, an ongoing trial by the University Hospital Southampton was expanded to increase asymptomatic testing among “a range of health and social care settings,” the BBC reported.

What does this mean for Kenya?

The less uncomfortable, inexpensive and quicker saliva test would be welcomed, as “people would be more open to do the test because it can be done from home and is not uncomfortable like the swab test,” says Eric Osoro, an epidemiologist. This would make targeted mass testing simpler, safer and with little or no resistance from the populace.

This non-invasive approach also comes as a relief to healthcare personnel as it eliminates the risk of exposure. “Since people are able to take their own samples, more resources can be deployed to getting supplies and conducting the tests,” he says.

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