At-home COVID-19 tests have become an easy way to self-diagnose. But current tests have drawbacks, such as the length of time it takes to get an answer, or how accurately the test can identify a positive case. And most of them require the uncomfortable procedure of sticking a swab up one’s nose. Now, researchers reporting in ACS Sensors have developed a SARS-CoV-2 saliva assay and prototype device that combine speed and ease with high sensitivity.
Non-invasive saliva-based tests exist, but they also rely on the slow and specialized RT-PCR approach. A similar method called reverse transcription loop-mediated isothermal amplification (RT-LAMP) can also detect viral SARS-CoV-2 RNA at a level of specificity and sensitivity consistent with RT-PCR, but it’s quicker, cheaper, and easier to use. Therefore, Weihua Guan and colleagues wanted to see if they could use RT-LAMP to create a fast and sensitive COVID-19 test that only requires a saliva sample; a palm-sized, portable device; and a smartphone.
The researchers integrated several steps into one compact machine, which they call the saliva-based SARS-CoV-2 self-testing with RT-LAMP in a mobile device (SLIDE). Its five distinct modules conduct all of the steps needed for RT-LAMP: heating the sample, mixing it with RT-LAMP reagents, carrying out the reaction, detecting how much viral RNA is present, and communicating that result to a smartphone.
To use SLIDE, a person simply spits into a vial on a cartridge that they insert into the device, and results are sent to a smartphone within 45 minutes. In lab tests, SLIDE successfully detected and quantitated a mock saliva sample spiked with inactivated SARS-CoV-2 virus particles, as well as a real saliva sample from someone known to be positive for COVID-19. In both cases, the results were consistent with those from RT-PCR, which suggests that the SLIDE device could be a quick, easy and sensitive way to tell whether someone has COVID-19, the researchers said.
Weihua Guan et. al, SLIDE: Saliva-based SARS-CoV-2 Self-Testing with RT-LAMP In a Mobile Device, ACS Sensors, 3-Aug-2022, 10.1021/acssensors.2c01023