Covid-19 test uses smartphone microscope for quick results

Researchers at the University of Arizona aim to combine the speed of existing nasal swab antigen tests with the high accuracy of nasal swab polymerase chain reaction (PCR) tests.

The researchers are adapting an inexpensive method that they originally created to detect norovirus using a smartphone microscope.

“We’ve outlined it so that other scientists can basically repeat what we did and create a norovirus-detecting device,” said researcher Lane Breshears.

“Our goal is that if you want to adapt it for something else, like we’ve adapted it for Covid-19, that you have all the ingredients you need to basically make your own device.”

Traditional methods for detection of norovirus or other pathogens are often expensive, involve a large suite of laboratory equipment and require scientific expertise.

The smartphone-based norovirus test consists of a smartphone, a simple microscope and a piece of microfluidic paper - a wax-coated paper that guides the liquid sample to flow through specific channels.

It is smaller and cheaper than other tests, with the components costing about $45 (£33). Users introduce antibodies with fluorescent beads to a potentially contaminated water sample.

If enough particles of the pathogen are present in the sample, several antibodies attach to each pathogen particle.

Under a microscope, the pathogen particles show up as little clumps of fluorescent beads, which the user can then count. The process - adding beads to the sample, soaking a piece of paper in the sample, then taking a smartphone photograph of it under a microscope and counting the beads - takes about 10 to 15 minutes.

The researchers believe the process is so simple that anyone could learn to do it with the help of an instructional video.

They are now fine-tuning it for adaptation towards Covid-19 detection. Students who are already being tested for Covid-19 on the Arizona campus through other methods will have the option to provide written consent for their sample to be run through the smartphone-based testing device as well.

“I have a couple of friends who had Covid-19 that were super-frustrated, because their PCR results were taking six or seven days or they were getting false negatives from rapid antigen tests. When they got the final PCR tests, they found out they had been sick, like they’d suspected,” said researcher Katie Sosnowski. “It’s really cool to be working on a detection platform that can get fast results that are also accurate.”