US-based scientists have developed an RNA-based breathalyser-style test that is capable of identifying people with Covid-19.
Dubbed the “Bubbler” by the Brown University researchers behind the project, the device relies on viral RNA detection to diagnose Covid-19. Its name is derived from the bubbling sound that occurs when the patient exhales into the device.
The Bubbler reverse transcribes RNA from airborne virus particles into DNA which can then be tested via PCR and can also be barcoded to allow samples to be linked directly to individual patients.
It can be used for simultaneous batches of pooled samples and provides additional information such as viral load and strain identity and eliminates the need for stabilising a sample.
“Involvement of the lower respiratory tract is often a precursor to severe Covid-19, so there is an argument for a more direct sampling focused on exhaled breath,” explained lead investigator Professor William G. Fairbrother of Brown University.
While virus detection by the Bubbler is similar to a hospital-swab PCR test the researchers believe it is a better measure of risk of contagion as it detects airborne viral particles. Swab tests can return a positive result for months after infection as they detect viral RNA fragments in cells that persist in previously infected cells. The Bubbler can also be adapted for environmental sampling in hospitals, transportation hubs, and closed environments like offices, ships, and planes, the investigators report.
Seventy patients treated in the Emergency Department of Rhode Island Hospital between May 2020 and January 2021 were screened.
The study tested samples from three points in the respiratory tract. Tongue scrapes from the mouth and from 15 seconds of exhaled breath collected in the Bubbler were compared to those from a conventional swab PCR test.
The Bubbler is a glass tube with a glass pipette through which patients can exhale. The tube is filled with a reverse transcription reaction mixture and cold mineral oil.
The study determined that not only can the virus can be readily detected in the breath; it is also more predictive of lower respiratory tract involvement.
“The Bubbler is more likely to be a better indicator of current infection than nasopharyngeal swabs,” said Fairbrother. “Another advantage is the barcoding, which enables high-throughput RNA virus testing at a fraction of the cost of conventional testing. The barcode returns a viral sequence that also supports strain identification, which may prove useful as more information is learned about transmissibility and possible strain-specific treatment decisions.”
The investigators also demonstrated how the Bubbler might be adapted to detect virus in airborne samples.
Last month, another team of researchers developed a prototype device that can tell with 95 per cent accuracy if someone is carrying certain viruses - a significant improvement over current rapid tests.