NEW DELHI: The dry swab RT-PCR test, that could cut down testing cost by four times and ramp up testing by 3 fold, does not show variance from standard testing method, said scientists.
The CSIR-CCMB team tested the stability of coronavirus samples on dry swabs, showing that the dry swabs can be stored in around 25 degree celsius and transported for up to 24 hours and needs no requirement of cold chain thereby cutting costs.
The samples are also stable for up to 3 days at 4 degree Celsius and the test results are comparable to that of the liquid Viral Transport Medium (VTM RNA), used at present. The study on temporal stability of the two strains of SARS-199 CoV-2 at two different temperatures indicates that, for shorter distance transportation cold chains can be avoided and the dry swab samples with low viral load also are stable at RT for 24 hours.
The dry swab method is expected to hold similar advantages in case of other emerging variants of SARS-CoV-2 as indicated by multiple sewage surveillance and sequencing studies.
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“The rapid spread and evolution of various strains of SARS-CoV-2, the virus responsible for COVID-19, continues to challenge the disease controlling measures globally. In this scenario, testing of maximum population in less time and minimum cost with existing diagnostic amenities is the only possible way to control the spread of the virus,” said the CCMB team in a paper in preprints.
The results collectively suggest that dry swab samples are stable at RT for 24 hours and the detection of SARS-CoV-2 RNA by RT-PCR do not show variance from VTM-RNA. This extraction free, direct RT-PCR method holds phenomenal standing in the present life-threatening circumstances due to SARS-CoV-2. As a measure to cut cost incurred per test, we optimised the minimum final concentration of proteinase K that can produce reliable results.
“This evidently suggests that the throughput of the tests can be increased four times in addition to bringing down the cost by four times. In conclusion, the dry swab method facilitates multiple advantages at the present critical time while the testing facilities are failing to cater the requirements. With the present testing facilities and resources, the dry swab method can increase the throughput of a lab by three-folds,” it said.
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