Automated PCR Home-Test Device Accurately Detects Covid-19 in Saliva

A recently developed saliva-based Covid-19 home test combines the simplicity and speed of rapid antigen tests with the accuracy of the gold-standard RT-PCR method.

Rapid antigen tests for the SARS-CoV-2 (Covid-19) antigen from nasal samples provide a fast (15 minutes) result. However, the sensitivity of antigen tests is 30 to 40% lower than nucleic acid testing (PCR), which could miss a significant portion of infected patients.

Image: The SLIDE device analyzes saliva and could help make COVID-19 testing quicker and easier (Photo courtesy of Dr. Weihua Guan, Pennsylvania State University)

With the problem of low sensitivity in mind, investigators at Pennsylvania State University (University Park, PA, USA) developed a fully integrated SARS-CoV-2 reverse transcription loop-mediated isothermal amplification (RT-LAMP) device (SLIDE) using a self-collected saliva sample. The five distinct modules of the SLIDE platform conducted 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 was present, and communicating that result to a smartphone.

The individual using the SLIDE platform simply projects saliva into a vial and onto a cartridge that is inserted into the device, and results are sent to a smartphone within 45 minutes.

The investigators reported that the SLIDE device achieved the limit of detection (LoD) of five copies/microliter of the saliva sample, which is comparable with the LoD (six copies/microliter) using FDA-approved quantitative real-time polymerase chain reaction (qRT-PCR) assays with the same heat-lysis saliva sample preparation method. With clinical samples, the SLIDE platform showed a good agreement with the results from the gold-standard RT-PCR method.

The investigators proposed that the SLIDE platform had great potential for performing self-administrated SARS-CoV-2 nucleic acid testing at home with noninvasive saliva samples.

The SLIDE device was described in the August 3, 2022, online edition of the journal ACS Sensors.

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