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Spit and scan. That’s all you need to do, and in under an hour you can not only tell if you have COVID-19 but which variant you have, all without leaving your home.
This is the hope and promise of a new saliva-based COVID-19 test that is currently in development.
“Several home tests are available to tell you if you have COVID-19, but none of them test for variants,” said study author Dr Xiao Tan, clinical researcher at the Wyss Institute for Biologically Inspired Engineering from Harvard University, Boston.
There are no plans to commercialize the test yet, but a new proof-of-concept study shows the technology works as well as benchmark PCR tests and could cost as little as $ 3 per test, which is much cheaper. than what is currently available. COVID-19 home tests.
The test, called Minimally Instrumented SHERLOCK, or miSHERLOCK, is based on CRISPR gene targeting technology. It only requires commercial chemicals, a 3D printer and commonly available equipment.
In contrast, COVID-19 tests based on PCR technology require highly specialized equipment and can take around four hours to get results. If a sample were to be tested for a specific variant using PCR technology, it would have to be genetically sequenced, which takes even more time and resources, Tan explained.
There are currently several COVID-19 home tests available. Some tests require samples to be sent to a lab for analysis, while others deliver results at home using various technologies such as test cards and processing fluids. No PCR test can be done at home.
So researchers from the Wyss Institute, the Massachusetts Institute of Technology, and several Boston-area hospitals collaborated to develop the new test.
For the study, the researchers tested saliva samples from 27 people with COVID-19 and 21 people without the virus. The test identified the virus about 96% of the time, which is comparable to PCR tests. In addition, the test detected three different variants of COVID-19: the British, South African and Brazilian variants.
The study was conducted before the Delta variant began to circulate widely, so it did not research this strain, but the technology can be quickly modified to detect additional variants, the researchers noted.
“Theoretically, you could find that you are positive for COVID-19, but negative for Delta all at the same time,” Tan said.
The test could also be used in areas that do not have access to genetic sequencing facilities, said study author Dr. Rose Lee, a pediatric teacher at Boston Children’s Hospital.
How it works
The new test is a simple battery-powered device that has two chambers: a heated sample preparation chamber and an unheated reaction chamber, Tan explained. A user spits into the sample preparation chamber, turns up the heat, and waits three to six minutes for the saliva to be absorbed into a filter.
Then you remove the filter and transfer it to the reaction chamber. “The virus is the key that unlocks the signal,” Tan said. “If there is no virus, there is no signal, but if there is a signal, it can be amplified.”
The results are easy to interpret. “If it turns green, you have COVID-19,” Tan said.
There is a chamber for the universal detection of COVID-19 and others that can be added to test the variants. “We imagine that a health authority would choose the most relevant variants in the region,” he said.
An accompanying app helps quantify the sample if the viral load is low and also offers an option to report the results, Tan said.
The study was published online on August 6 in the journal Scientists progress.
Experts not involved in the study said many questions remain about the role this type of testing can play in the ongoing pandemic.
“This is the first point-of-care test that can determine variants, and it can be adapted to other types of variants as they emerge,” said Dr. Jeffrey SoRelle, pathologist at the University of Texas Southwestern Medical Center, Dallas. . “There is no difference in management depending on the variant, but it is possible that a variant will require us to change our treatment in the future.”
Dr Heba Mostafa, assistant professor of pathology and director of the molecular virology laboratory at Johns Hopkins Medicine in Baltimore, agreed. “The question is how valuable it is to have a point-of-care test that targets a specific variant, and the answer is not clear because the variants are not exploitable for patient management,” said she declared.
Such information is more useful on a larger scale to better track mutations as they spread across the world, Mostafa added.
More information
Visit the U.S. Centers for Disease Control and Prevention to learn more about COVID variants.
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