Home test for Covid-19 boasts PCR accuracy using saliva sample

A Covid-19 test that can be used at home and is as accurate as a polymerase chain reaction (PCR) test has been developed by researchers at Pennsylvania State University.

At-home tests have become an easy way to self-diagnose Covid-19, but tests such as the commonly used lateral flow have drawbacks, such as the length of time it takes to get an answer, or how accurately the test can identify a positive case.

Most of them also require the uncomfortable procedure of sticking a swab up one’s nose.

Though PCR tests are known as the “gold-standard” because of their high sensitivity and specificity for Covid-19, it requires the sample to be sent away to a lab and be analysed by specialised personnel.

The analysis itself can take up to an hour, but the total time from swab to answer can take days.

 The SLIDE device analyzes saliva and could help make COVID-19 testing quicker and easier.

Image credit: Weihua Guan

The prototype device combines speed with PCR levels of sensitivity while only requiring a saliva sample, a palm-sized, portable device and a smartphone.

It uses a method called reverse transcription loop-mediated isothermal amplification (RT-LAMP) which can also detect Covid-19 at a level of specificity and sensitivity consistent with PCR, but is quicker, cheaper and easier to use.

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 Covid-19 virus particles, as well as a real saliva sample from someone known to be positive for the virus.

In both cases, the results were consistent with those from 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.

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