Scientists have developed a portable saliva-based smartphone testing platform for COVID-19 which they claim can provide results within 15 minutes without the need for resource-intensive laboratory methods.

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The new approach, described in the journal Science Advances, pairs a fluorescence microscope readout device with a smartphone to determine the quantity of virus in a patient sample. In the study, the scientists, including Bo Ning from Tulane University School of Medicine in the US, used an assay made of CRISPR/Cas12a molecules to test 12 people infected with the novel coronavirus and six healthy controls, which was then read out using the smartphone platform.

According to the researchers, the technique works as effectively as the well-established RT-PCR method. "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," the scientists wrote in the study.

While most COVID-19 tests currently require swabbing the upper part of the throat behind the nose, requiring medical professionals in full protective gear to collect samples before running tests, the scientists said the SARS-CoV-2 virus may be equally present in the saliva during early infection. They said saliva-based COVID-19 tests could enable comparably reliable but simpler and safer testing.

To develop the platform for saliva-based testing, the researchers built a prototype assay chip that uses CRISPR/Cas12a molecules to better detect the viral genetic material within a saliva sample. They integrated this 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 6 healthy controls, and found that the approach successfully distinguished between patients with and without the virus. When they compared nasal and saliva swabs from non-human primates before and after infection, the scientists found higher levels of the viral RNA in the saliva swabs. Based on this finding, the researchers suggested that saliva may provide a robust means of diagnosis after infection. The scientists believe that a future version of the chip used in this technique could contain pre-loaded reagents and sample controls, and a custom smartphone app could enable secure and wireless test data reporting.