Smartphone-Read Ultrasensitive and Quantitative Saliva Test for COVID-19 Provides Results within 15 Minutes

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, the researchers 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 6 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. The researchers 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.

"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 wrote.