Researchers at the US National Institutes of Health (NIH) have created a sample preparation method that could reduce the time and cost required to test for the coronavirus (Covid-19).
The method allows the virus to be detected without needing to extract SARS-CoV-2 genetic ribonucleic acid (RNA) material.
It was developed through a partnership among scientists at the National Eye Institute (NEI), the NIH Clinical Centre (CC) and the National Institute of Dental and Craniofacial Research (NIDCR).
Traditional Covid-19 tests require viral RNA to be extracted and amplified to detectable levels using a quantitative reverse transcription-polymerase chain reaction (RT-qPCR) technique.
The NIH researchers tested several chemicals using synthetic and human samples to detect agents that could preserve SARS-CoV-2 RNA in samples with little degradation and allow the virus to be identified directly by RT-qPCR.
The team used Chelex 100 resin, a chelating agent produced by lab supply company Bio-Rad, to preserve the viral RNA in specimens for RT-qPCR detection.
NEI Ophthalmic Genomics Laboratory fellow Bin Guan said: “We used nasopharyngeal and saliva samples with various virion concentrations to evaluate whether they could be used for direct RNA detection.
“The answer was yes, with markedly high sensitivity. Also, this preparation inactivated the virus, making it safer for lab personnel to handle positive samples.”
To validate the test, patient samples were collected and stored in either viral transport media or the new chelating-resin buffer.
The samples in viral transport media were analysed using standard RNA extraction and RT-qPCR testing, while specimens in the chelating-resin buffer were heated and the viral RNA was tested by RT-qPCR.
Findings showed that the new method allowed a lot more RNA yield to be tested compared with the conventional approach.
NEI Medical Genetics and Ophthalmic Genomic Unit chief Robert Hufnagel said: “We think this novel methodology has clear benefits of increasing sensitivity, cost and time savings for testing.
“The method stabilises the RNA at room temperature for easier transport, storage and handling in clinical settings.”
Last month, an NIH study found that the effectiveness of rapid antigen tests was comparable to that of laboratory-based PCR tests for Covid-19 serial screening when used every three days.