An inexpensive, compact version of equipment that is usually bulky and costly can find the coronavirus in saliva with the accuracy of a PCR test and the speed of rapid antigen tests, according to Spanish researchers.

The experimental device employs flow cytometry, which uses lasers to count and sort cells and particles in liquid as it flows through a very small tube.

The saliva is mixed with a solution containing fluorescent antibodies that attach themselves to any coronavirus particles.

After about 20 minutes, the liquid gets passed through the tube, where lasers will detect any fluorescence and trigger a positive reading, the researchers explained on Tuesday in Biomedical Optics Express.

When they tested saliva samples from 34 people with SARS-CoV-2 infections and 20 uninfected individuals, the device was 91.2 per cent accurate at detecting the virus and 90 per cent accurate at identifying uninfected individuals.

It was also able to find the virus at much lower concentrations than can be detected with rapid antigen tests, according to the report.

“Given the results, we believe that our (equipment) in conjunction with saliva samples has great potential for becoming a fast, portable, user-friendly point-of-care device, able to perform up to 2000 tests per day,” the researchers concluded.

“By selecting proper antibodies, this technology could also be adapted for the detection of other viruses, such as … influenza virus, or even microorganisms in water, such as Legionella and E-coli,” coauthor Ewelina Wajs of The Institute of Photonic Sciences in Barcelona, said in a statement.