Scientists in Singapore have developed a handheld breathalyser test that can non-invasively diagnose Covid-19 cases, even in asymptomatic individuals, in less than five minutes, the Press Trust of India reported. Described in the ACS Nano journal, the test will allow rapid screening of people at large gatherings. Currently, the RT-PCR is the gold standard for Covid-19 testing.
However, Nanyang Technological University researchers noted that the RT-PCR method was slow and required an uncomfortable nasopharyngeal swab in a laboratory scenario. On the other hand, while the rapid antigen test (RAT) provides quicker results, it has a higher rate of false positives and negatives.
The team wanted to develop a convenient and accurate breathalyser test that would deliver quick results and was suitable for on-site screening.
The handheld breathalyser contains a chip with three surface-enhanced Raman scattering (SERS) sensors that is attached to silver nanocubes. When a person breathes into the breathalyser, compounds in the breath interact chemically with the sensors. The breathalyser is then loaded into a portable Raman spectrometer, which characterises the bound compounds on the basis of changes to the molecular vibrations of the SERS sensors.
The scientists found that the Raman spectra from Covid-positive and -negative people were different in regions responsive to alcohols, ketones, and aldehydes. These results were then used to develop a statistical model to diagnose Covid-19 cases.
Previous breathalyser-type tests relied on differences in concentrations of volatile organic compounds exhaled by infected patients. However, most of these tests required bulky, nonportable instruments.
The new breathalyser was tested on 501 people in Singapore’s airports and hospitals. RT-PCR test showed the participants to be negative (85.2%), positive and symptomatic (8.6%), or positive and asymptomatic (6.2%).
The breathalyser had a 3.8% false-negative and 0.1% false-positive rate, which is comparable to RT-PCR tests. However, the breathalyser device can be completed on-site in less than five minutes.
The researchers said the breathalyser could someday be a new tool to reduce the silent community spread of Covid-19.
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