Scientists have developed a portable saliva-based smartphone platform for rapid Covid-19 testing that they claim can provide results within 15 minutes without the resource-intensive laboratory tests. The new technique detailed in the journal Science Advances pairs a fluorescence microscope readout device with a smartphone to determine viral load from a CRISPR/Cas12a assay.
The new test works as effectively as the well-established quantitative reverse-transcriptase polymerase chain reaction method, the experiments in a small number of participants showed.
The authors wrote, "We believe this smartphone platform, a similar future application, offers the potential to rapidly expand Covid-19 screening capacity, and potentially simplify the verification of contact tracing, to improve local containment and inform regional disease control efforts.”
Most Coronavirus tests currently require swabbing the upper part of the throat behind the nose -- an uncomfortable process that requires medical professionals in full protective gear to collect samples in airborne infection isolation rooms before running RT-PCR tests.
However, recent studies have found that SARS-CoV-2, the virus responsible for Covid-19, may be equally present in the nasopharynx and the saliva during early infection, suggesting saliva-based Covid-19 tests could enable comparably reliable but simpler, safer testing.
To develop a widely accessible platform for saliva-based testing, Bo Ning from Tulane University School of Medicine in the US and colleagues built a prototype assay chip that uses the CRISPR/Cas12a enzyme to enhance an amplified viral RNA target's signal within a saliva sample.
They integrated the chip into a smartphone-based fluorescence microscope readout device, which captures and analyses images to determine whether the virus is present above a threshold concentration. The researchers used this design to analyse saliva from 12 patients with Covid-19 and six healthy controls, finding that the approach successfully distinguished between patients with and without the virus.
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Additionally, the researchers compared nasal and saliva swabs from non-human primates before and after infection.
They found higher SARS-CoV-2 RNA levels in the saliva swabs, further suggesting that saliva may provide a robust means of diagnosis after infection.