Fast, Cheap Test Detects COVID-19 Virus’ Genome without Need for PCR

Researchers have developed a new test for COVID-19 that combines the speed of over-the-counter antigen tests with the accuracy of PCR tests that are processed in medical labs and hospitals.

The Harmony COVID-19 test developed by researchers at the University of Washington (Seattle, WA, USA) is a diagnostic test that, like PCR tests for COVID-19, detects genetic material from the SARS-CoV-2 virus. But whereas conventional PCR tests can take several hours, the Harmony kit can provide results in less than 20 minutes for some samples and with similar accuracy.

The researchers developed Harmony to be simple and easy-to-use, employing ready-to-use reagents. The test uses a “PCR-like” method to detect the presence of the SARS-CoV-2 RNA genome in a nasal swab sample with the aid of a small, low-cost detector, which was also designed by Lutz’s group. A smartphone is used to operate the detector and read the results. The detector can handle up to four samples at a time and would fit into a standard car’s glove compartment.

Many at-home antigen kits for COVID-19, which detect pieces of the proteins the virus creates instead of its genetic material, are 80-85% accurate, though accuracy may drop with the omicron variant, which harbors a relatively high number of mutations not found in other strains. PCR - or polymerase chain reaction - tests are generally 95% accurate or better but require expensive equipment and a long wait for results.

Initial results show that the Harmony kit is 97% accurate for nasal swabs. The Harmony kit detects three different regions of the virus’ genome. If a new variant has many mutations in one region, the new test can still detect the other two. It can, for example, detect the omicron variant, which has dozens of mutations in the region of the genome that encodes the so-called spike protein. Though tests based on PCR are highly accurate, a key limitation is that PCR tests require dozens of cycles of heating and cooling to detect genetic material in a sample. The Harmony test sidesteps this issue by relying on a PCR-like method known as RT-LAMP, which doesn’t have the same stringent temperature-cycling requirements.

“We designed the test to be low-cost and simple enough that it could be used anywhere,” said Barry Lutz, a UW associate professor of bioengineering and investigator with the Brotman Baty Institute for Precision Medicine. “We hope that the low cost will make high-performance testing more accessible locally and around the world.”

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