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

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.

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.