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

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

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

saliva-based COVID-19 diagsis offers an improvement over standard nasopharyngeal swab methods because people can collect ir 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 t require a separate nucleic acid (RNA) extraction step. This is significant because extraction kits used for this step in or tests have been prone to shorts in past,” A R Anand, senior associate professor at Chennai’s L&T Microbiology Research Centre, told PTI.

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

Discussion on techlogy intensified after US Food and Drug ministration (FDA) this week gave Yale School of Public Health emergency use authorisation for its ‘Salivirect’ COVID-19 diagstic test.

  FDA said in a statement that Salivirect does t require any special 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 matter be explored furr.

“A fast-tracked 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,” Anand said.

  An Indian Council of Medical Research (ICMR) scientist ded that India is exploring availability of kits and or aspects. “At present, kit is approved in India," he said on condition of anymity.

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

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

re are two s of diagstic tests for COVID-19 testing, both using swabs from se and throat.

 RT-PCR test, which can take hours or even days before a result, detects genetic material of virus using a lab technique called polymerase chain reaction.  second diagstic test, antigen COVID-19 test, detects certain proteins in virus. An antigen test can also produce results in minutes.

Saliva tests would be an improvement on both.

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

“Such systems also reduce 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 ded.

Vineeta Bal, an immulogist 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 ‘rmal’ that we knew of before pandemic. In India, some researchers are developing tests for detection from saliva. But as far as I kw y are far from reaching market,” Bal ded.

ting pluses of Yale saliva test, virologist Shahid Jameel pointed to ease of sample collection and reduced cost for extracting RNA, genetic material of a virus. It would also le to fewer false negative results.

“Most false negative results in RT-PCR test today are due to improper sampling from nasopharyngeal area, which is also uncomfortable for person being tested,”Jameel, CEO of Wellcome Trust/DBT India Alliance, a public charity that invests in building biomedical sciences, told PTI.

In dition to Yale saliva test, Israel’s Center for Geographic Medicine and Tropical Diseases has developed a  test that aims to determine in less than a second wher a person is infected with vel coronavirus.

ting that Israel test is yet to be approved, Jameel said it uses scattering of light by virus particles in mouth washings to estimate both presence or absence, and quantity of virus particles in sample.

“This is based on obtaining data from a large number of positive and negative people and training an algorithm to pick right scattering patterns. Besides light source, this test uses artificial intelligence (AI) and machine learning, hoping to get better with time as more samples are analysed,” Jameel explained.

Machine learning is  an application of AI that provides systems ability to automatically learn and improve from experience.

“Both   tests will reduce time. Yale test will only cut RNA extraction time as rest of process is same. Israel test is very quick,” Jameel ded.

Virologist T Jacob John agreed that  saliva test is a low-cost alternative.

Explaining one of ways in which saliva test can work, he said, “re is a process of viral genetic material (RNA) converted to DNA, which is n detected by a method different from PCR. It is called ‘loop-mediated isormal amplification’, or LAMP, an original Japanese invention,” John, former he of clinical virology at Christian Medical College, Vellore, told PTI.

LAMP is a cheaper PCR alternative previously used to detect outbreaks of zika and ebola in resource-poor countries.

“ final reing is taken by colour reaction -- pink turning to yellow. equipment is cheaper than PCR equipment… If spit is collected, it avoids use of special swabs which are in short supply,“ said John.

Israel and India are conducting trials here on a large sample of patients for four different kinds of techlogies, including two COVID-19 tests that could give results in minutes from a saliva sample, according to a statement by Israeli Embassy in Delhi.