COVID-19 saliva diagnosis cheaper, faster alternative to swab testing, say scientists


NEW DELHI: A low-cost saliva test that will enable people to collect their own samples with minimal discomfort, without invasive nasal or throat swabs, could well be the way forward to detect the novel coronavirus, say scientists.

Giving a thumbs up to the alternative testing technology that is yet to be introduced in India, scientists said it would deliver results faster and more accurately and also minimise the risk for healthcare workers collecting samples.

The saliva-based COVID-19 diagnosis offers an improvement over standard nasopharyngeal swab methods because people can collect their own samples with ease — simply spit into a sterile tube and mail it to a lab for processing.

“It is also unique because it does not require a separate nucleic acid (RNA) extraction step. This is significant because the extraction kits used for this step in other tests have been prone to shortages in the past,” A R Anand, senior associate professor at Chennai’s L&T Microbiology Research Centre, told PTI.

Noting that the ‘saliva direct’ test is easier to carry out, he said it needs only a few reagents and a real-time polymerase chain reaction (RT-PCR) machine.

Discussion on the technology intensified after the US Food and Drug Administration (FDA) this week gave the Yale School of Public Health emergency use authorisation for its ‘Salivadirect’ COVID-19 diagnostic test.

The FDA said in a statement that SalivaDirect does not require any special type of swab or collection device.

A saliva sample, it said, can be collected in any sterile container.

Though saliva tests are yet to be approved in India for mass use, scientists such as Anand suggest the matter be explored further.

“A fast-tracked study should be conducted in an Indian setting comparing the saliva RT-PCR tests with the nasopharyngeal RT-PCR tests before large-scale implementation in our country,” Anand said.

An Indian Council of Medical Research (ICMR) scientist added that India is exploring the availability of kits and other aspects.

“At present, no kit is approved in India,” he said on the condition of anonymity.

According to a recent study published in ICMR’s Indian Journal of Medical Research, gargled water samples may be another viable alternative to swabs for detecting COVID-19, enabling easy self-collection and removing the need for trained healthcare workers for sample collection.

Asked about the saliva test cleared by the FDA, ICMR Director General Balram Bhargava on Wednesday told a parliamentary panel that taking samples from gargled water is already under consideration and further details will be available soon.

There are two types of diagnostic tests for COVID-19 testing, both using swabs from the nose and the throat.

The RT-PCR test, which can take hours or even days before a result, detects genetic material of the virus using a lab technique called polymerase chain reaction.

The second diagnostic test, the antigen COVID-19 test, detects certain proteins in the virus.

An antigen test can also produce results in minutes.

Saliva tests would be an improvement on both.

“The collection does not involve material such as swabs — which can be in short supply — and the person doing the collection does not need as much training,” Satyajit Rath, from New Delhi’s National Institute of Immunology, told PTI.

“Such systems also reduce the cost since we don’t have to depend on one company. Saliva is a much easier sample to collect from patients, compared to nasopharyngeal swabs, which are a little invasive and cause some discomfort to patients,” Anand added.

Vineeta Bal, an immunologist from Pune’s Indian Institute of Science, Education and Research, said saliva tests might become easily accessible like rapid paper strip tests available for testing blood or urine glucose.

“Hence, life can come closer to the ‘normal’ that we knew of before the pandemic. In India, some researchers are developing the tests for detection from saliva. But as far as I know they are far from reaching the market,” Bal added.

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