Covid-19 saliva diagnosis is cheaper, faster alternative to swab tests, scientists say


NEW DELHI: A low-cost saliva test that will allow people to collect their own samples with minimal discomfort, without invasive nasal or throat swabs, may well be the way forward to detect the novel coronavirus, scientists say .
Taking a look at alternative testing technology that has yet to be introduced in India, scientists said it will deliver results faster and more accurately and also minimize the risk to healthcare workers of collect samples.
The saliva-based diagnosis of Covid-19 offers an improvement over standard nasopharyngeal sampling methods, as people can easily collect their own samples – just spit them out in a sterile tube and mail it to a laboratory for processing. “It’s also unique because it doesn’t require a separate nucleic acid (RNA) extraction step. This is important because the extraction kits used for this step in other tests have been subject to shortages in the past, AR Anand, senior associate professor at Chennai’s L&T Microbiology Research Center, told PTI. Noting that the “direct saliva” test is easier to perform, he said it only required a few reagents and a real-time polymerase chain reaction (RT-PCR) machine.
Discussion of the technology intensified after the United States Food and Drug Administration (FDA) this week granted the Yale School of Public Health emergency use clearance for its Covid-19 diagnostic test “Salivadirect”. The FDA said in a statement that SalivaDirect does not require any special type of swab or collection device. A saliva sample, he says, can be collected in any sterile container.
Although saliva testing has yet to be approved in India for mass use, scientists such as Anand suggest the issue be further explored.
“An accelerated study should be conducted in an Indian setting comparing saliva RT-PCR tests with nasopharyngeal RT-PCR tests before large-scale implementation in our country,” said Anand. A scientist from the Indian Council for Medical Research (ICMR) added that India is studying the availability of the kits and other aspects. At present, no kit is approved in India, ”he said on condition of anonymity.
Gargle water samples may be another viable alternative to swabs for detecting Covid-19, allowing easy self-collection and eliminating the need for personnel, according to a recent study published in the Indian Journal of Medical Research by ICMR. qualified health worker to collect samples.
Asked about the FDA-cleared saliva test, ICMR chief executive Balram Bhargava told a parliamentary panel on Wednesday that gargling water samples were already under consideration and more details would be forthcoming. available soon.
There are two types of diagnostic tests for the Covid-19 test, both using swabs from the nose and throat.
The RT-PCR test, which can take hours or even days before a result, detects the genetic material of the virus using a lab technique called a polymerase chain reaction. The second diagnostic test, the Covid-19 antigen test, detects certain proteins of the virus. An antigen test can also produce results within minutes.
The saliva tests would be an improvement in both cases.
“The collection does not involve such equipment as swabs – which can be scarce – and the person doing the collection does not need as much training,” said Satyajit Rath, of the National Institute of Immunology of New Delhi, at PTI.
“Such systems also reduce costs because we don’t need to depend on a single company. Saliva is a much easier sample to take from patients, compared to nasopharyngeal swabs, which are somewhat invasive and cause some discomfort to patients, ”added Anand. .
Vineeta Bal, an immunologist at the Indian Institute of Science, Education and Research in Pune, said saliva tests could become easily accessible, as rapid paper strip tests available to test for blood glucose or urinary.
“As a result, life can get closer to the ‘normal’ we knew before the pandemic. In India, some researchers are developing tests to detect saliva. But as far as I know, they’re a long way from hitting the market, ”Bal added.
Noting the benefits of the Yale saliva test, virologist Shahid Jameel pointed out the ease of sample collection and the reduced cost of extracting RNA, the genetic material of a virus. It would also result in fewer false negatives.
“Most of the false negative results of the RT-PCR test today are due to improper sampling of the nasopharyngeal area, which is also uncomfortable for the person being tested,” Jameel, CEO of Wellcome Trust / DBT India Alliance, an organization public charity that invests in building biomedical sciences, PTI said.
In addition to Yale’s saliva test, the Israel Center for Geographic Medicine and Tropical Diseases has developed a test that aims to determine in less than a second whether a person is infected with the novel coronavirus.
Noting that the Israeli test has not yet been approved, Jameel said he uses light scattering from viral particles in mouthwashes to estimate both the presence or absence and the amount of particles. virus in the sample.
“This is based on getting data from a large number of positive and negative people and training an algorithm to choose the right delivery models. Besides the light source, this test uses artificial intelligence (AI) and machine learning, hoping to improve over time. as more samples are analyzed, ”Jameel explained.
Machine learning is an application of AI that enables systems to learn and improve automatically from experience.
“Both tests will reduce the time. The Yale test will only reduce the RNA extraction time because the rest of the process is the same. Israel’s test is very quick, ”Jameel added.
Virologist T Jacob John agreed that the saliva test is an inexpensive alternative.
Explaining one of the ways the saliva test can work, he said, “There is a process of converting viral genetic material (RNA) into DNA, which is then detected by a method other than PCR. It’s called “isothermal loop-mediated amplification,” or LAMP, an original Japanese invention, John, former chief of clinical virology at Christian Medical College, Vellore, told PTI.
LAMP is an alternative to the cheaper PCR previously used to detect zika and Ebola outbreaks in resource-poor countries.
“The final reading is taken by color reaction – pink turns yellow. The equipment is less expensive than PCR equipment… If the pin is collected, it avoids the use of special swabs which are rare, ”John said.
Israel and India are conducting trials here on a large sample of patients for four different types of technology, including two Covid-19 tests that could give results within minutes from a saliva sample, according to a statement from the Israeli Embassy in Delhi.


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