New diagnostic test for COVID-19 can deliver results in half an hour

Researchers from the Karolinska Institute in Sweden, together with researchers in China, developed a new diagnostic test for COVID-19. The test can be done without advanced laboratory equipment and deliver the result in about half an hour, according to a study published in the journal. Clinical Chemistry. Investigators are now working to verify test results on COVID-19 confirmed patients at Karolinska University Hospital.

Currently, so-called PCR tests are routinely used to assess whether a patient has been infected with COVID-19, the disease caused by the new coronavirus that has spread like a wildfire worldwide. The PCR method allows very small amounts of a pathogen to be found. However, the tests require trained personnel and sophisticated laboratory equipment that can alternate between different temperatures, and it takes at least two hours to get a result. Therefore, there is a significant need for rapid and accurate testing methods for COVID-19 that can be carried out on site also during basic conditions.

Now, researchers from the Karolinska Institutet, along with researchers from Shenyang University of Chemical Technology and Huazhong University of Science and Technology in China, developed a COVID-19 experimental test with promising results.

The researchers have adapted a technique called loop-mediated isothermal amplification (LAMP) specifically for the new coronavirus. The technique allows the virus RNA to be amplified at a constant temperature of 65 degrees Celsius and to see a reaction in just 20 to 40 minutes.

It can be done under simple conditions

“A great advantage of our test is that it is fast and can be performed under basic conditions,” says Vicent Pelechano, a researcher at the Department of Microbiology, Tumor and Cell Biology and SciLifeLab at the Karolinska Institute and one of the study authors. “All you need is a test tube containing the primers, a hot plate, a thermometer and a water pot. This makes it especially suitable for regions that lack advanced analytical equipment, such as war-torn areas or fields of refugees”.

By combining primers optimized specifically for SARS-CoV-2 with a virus-specific gene, the researchers were able to detect as few as 10 copies of the virus gene, which is in line with the detection limits of the PCR method. The technique can be combined with a pH indicator, which changes the color of the reaction mixture from pink (alkaline) to yellow (acid) if the sample is positive for SARS-CoV-2.

“The color indicator makes it extremely easy to see if a sample is positive or negative,” says Vicent Pelechano. “That could be a deciding factor if he lacks specialized equipment to verify the reaction.”

Most of the study was carried out using optimized genetic sequences of the virus. In addition, a total of 248 samples from COVID-19 confirmed patients in China were analyzed, of which 89.9 percent tested positive with the LAMP test. The remaining 10.1 percent were considered to have viral loads so low that they were negative.

Verification studies ongoing

Further research is currently underway at Karolinska University Hospital to verify that the test works in real patients whose samples have not been purified by extraction of a specific gene from the virus.

“We have shown that this technique works under optimal conditions in the laboratory, and we have seen promising results from the first studies in patients in China,” says Vicent Pelechano. “Now we have to make sure that the test works in other conditions as well, like in real patients with COVID-19 in Sweden.”

The researchers plan to make the reagents widely available to the community. The primers used in this document can be requested for free delivery at [email protected].