COVID-19 FAQ: What Are Saliva Tests and How Do They Work?

In a recent development, the US Food and Drug Administration (FDA) gave emergency approval to a new method of testing for COVID-19. This new diagnostic test that uses saliva samples has been termed as “ground-breaking” by the FDA.

The saliva-based diagnostic tests may soon be conducted in India for the detection of COVID-19, if the government deems that the process is safer for healthcare workers and less discomforting for individuals.

Here’s what you should know about these new saliva-based diagnostic tests:

What is the saliva-based diagnostic test and how does it work?

Like the currently used RT-PCR test, a saliva-based diagnostic test for COVID-19 too detects the presence of the virus. It converts the viral RNA into DNA, and then amplifies the DNA for the detection of the pathogen.

The saliva-based tests are not rapid or at-home diagnostic tests which can be self-administered. These tests follow the conventional molecular test that is the gold standard for COVID-19 diagnosis.

Is the saliva test better than the diagnostic tests being used currently?

The currently used method of sample collection is invasive in nature, as it requires healthcare workers to insert a diagnostic tool into the throat of an individual. In the saliva-based method, individuals can simply spit into a collection kit, which will then be handed over to the lab for diagnosis.

This reduces not only the level of discomfort for the patient, but also the risk posed to the healthcare worker administering the test. This will reduce the currently heavy reliance on PPE gear for medical personnel.

“We have completed our trial and found that saliva is an equally good sample as nasopharyngeal for RT PCR (reverse transcriptase polymerase chain reaction) test, with much less problems to the patient and healthcare professionals,” said Vikas Deswal, Consultant – Internal Medicine, at Medanta Hospital in Gurgaon, according to an Economic Times report.

“We collected the samples by a drooling method in a tube... in fact, in our observation, the accuracy was better than the present method of testing,” Deswal said.

Are there any drawbacks to the saliva-based diagnostic test?

The saliva-based test does have some limitations. Negative results obtained from this test do not rule out out the possibility of the SARS-CoV-2 infection. The results then need to be complemented by further clinical observations. Moreover, if the saliva obtained from the patients contains blood or mucus, it can be difficult to pipet.

What approvals has the saliva test received in the US?

According to a report by The Indian Express, The US Food and Drug Administration (FDA) issued an emergency-use authorisation to Yale School of Public Health’s diagnostic kit, called SalivaDirect. This is the fifth test using saliva as a sample for testing that the USFDA has approved.

The trials for the test were initially conducted on a group of basketball players from the NBA (National Basketball Association) and its support staff. It has now been validated for the diagnosis of asymptomatic individuals.

Will the saliva-based test be used in India?

The researchers from Medanta Hospital seek to publish their study in a medical journal and plan to approach the Indian Council of Medical Research (ICMR) in two weeks to request permission for this method of sample collection.

TransAsia Bio is also starting a trial to get saliva samples validated by ICMR. “We will be doing an internal evaluation and in a month’s time will reach out to the authorities with out findings,” Suresh Vazirani, MD of TransAsia Bio told the Economic Times.