Researchers tested the new method using 215 COVID samples that RT-PCR showed positive (pictorial)
Washington:
Scientists have developed a new method of testing COVID-19 that does not use key reagents but still provides an accurate result, an advancement that may lead to an inexpensive diagnostic technique in developing countries where chemical supplies are rare.
The method, described in the journal PLOS Biology, omits the step of the widely used reverse transcription polymerase chain reaction (RT-PCR) assay where scarce reagents are needed, but has 92% accuracy, missing only the lowest viral loads. .
Researchers, including those at the University of Washington in the United States, tested the new method using 215 samples of COVID-19 that RT-PCR tests had shown positive, with a range of viral loads, and 30 that were negative.
They said he correctly identified 92 percent of positive samples and 100 percent of negatives.
While the positive samples the new test failed to capture had very low levels of the virus, scientists said ultra-sensitive tests that identify individuals with even the smallest viral load may not be. not needed to slow the spread of disease.
“It was a very positive result,” said Jason Botten, lead author of the study from the University of Vermont in the United States.
“You can go for the perfect test, or you can use the one that will capture the vast majority of people and stop the transmission,” Botten said.
While standard PCR tests have three steps, the version developed by the researchers has only two, the study noted.
“In step 1 of the RT-PCR test, you take the swab with the nasal sample, cut off the end and place it in a vial of liquid or medium. Any virus present on the swab will be transferred from swab around the middle, ”Botten says.
“In step 2, you take a small sample of the medium containing the virus and use chemical reagents, often rare ones, to extract the viral RNA. In step 3, you use other chemicals to dramatically amplify any viral genetics, material that might be there. If the virus were present, you would get a positive signal, “he explained.
In the new method, Botten said, a sample of the medium that contained the nasal swab is taken directly to the third amplification step, which eliminates the need for scarce RNA extraction reagents and dramatically reduces time, the labor and costs required for extraction. Viral RNA from the middle to step 2.
According to the researchers, the test is ideally suited for screening programs in both developed and developing countries because it is “inexpensive, takes much less processing time and reliably identifies those who are likely to spread the disease “.
Its low cost and effectiveness could extend testing capacity to groups that are not currently being tested, including asymptomatic nursing home residents, essential workers and school children, Botten added.
He said the standard RT-PCR test could be reserved for groups, such as healthcare workers, for whom near 100% accuracy is essential.
