Offering an ultrasensitive yet accessible approach to COVID-19 testing, a portable saliva-based smartphone platform provides results within 15 minutes without the resource-intensive laboratory tests the current gold standard requires, according to a new study.
The approach was tested in 12 people infected with COVID-19 and six healthy controls. Bo Ning and colleagues demonstrate that this technique, which pairs a fluorescence microscope readout device with a smartphone to determine viral load from a CRISPR/Cas12a assay, works as effectively as the well-established quantitative reverse-transcriptase polymerase chain reaction (RT-qPCR) 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 authors write.
Most COVID-19 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-qPCR tests.
However, recent studies have found that SARS-CoV-2 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, Ning 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 analyzes images to determine whether the virus is present above a threshold concentration.
The researchers used this design to analyze saliva from 12 patients with COVID-19 and six healthy controls, finding that the approach successfully distinguished between patients with and without the virus. 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. Ning and colleagues anticipate 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, wireless test data reporting to support telehealth efforts.
- This press release was provided by the American Association for the Advancement of Science
