A new test developed by researchers can detect infection with COVID-19 in 30-45 min in urine, blood and saliva.
The standard test that has been used for confirming infection with SARS-CoV-2 to date is quantitative reverse transcription (qRT) PCR—a commonly used lab technique, but one that requires expensive equipment and experienced users to perform.
Although qRT-PCR is a reliable test, it can take time for test results to be available. As reported in the journal PLoS ONE, Laura Lamb, Ph.D., and colleagues based at the Beaumont Health System in Michigan, have developed a test using a different method known as Reverse Transcription Loop-Mediated Isothermal Amplification or RT-LAMP.
“Currently, clinical testing for SARS-CoV-2 is done by central testing laboratories, which may take one or more days,” write the authors.
“Point-of-care testing should be fast, easy to use by a range of users, low cost, and require little if any laboratory infrastructure.”
Similar to RT-PCR, RT-LAMP is a technique that has been developed to amplify RNA rather than DNA. It was developed to be simpler and cheaper than PCR, as it does not require the repeated heating cycles of PCR and just requires warming in a hot water bath. It has great potential for infectious disease diagnosis. It can be stored at room temperature, can be done in a single tube, and can also be color-marked so that the mixture changes color if the target RNA is present—making diagnostic testing easier for non-experts.
In this study, the researchers added fragments of SARS-CoV-2 sequence to human serum, urine and saliva samples, as well as nose and throat swabs and then used RT-LAMP to test the samples. They also tested RNA isolated from nose swabs taken from COVID-19 patients. They checked the accuracy of their test by comparison to qRT-PCR and tested specificity of the RT-LAMP test by checking against other related coronaviruses.
The team found that their test accurately detected SARS-CoV-2 in both the simulated samples and the COVID-19 patient samples in 30-45 minutes.
The researchers tested the same RNA samples from 20 patients that had been confirmed to have COVID-19 using qRT-PCR and 20 samples from patients that tested negative. The RT-LAMP test was 95% (19/20 patients) accurate at detecting positive samples and 90% (18/20 patients) accurate at detecting negative samples.
Although this test requires extra validation before it can be used more widely, the researchers believe it has the potential to make testing for COVID-19 much quicker, easier and more cost effective.
“This simple assay could be used outside of a central laboratory on various types of biological samples. [It] can be completed by individuals without specialty training or equipment and may provide a new diagnostic strategy for combatting the spread of SARS-CoV-2 at the point-of-risk,” conclude the authors.
The Michigan team is not the first to realise the potential of the RT-LAMP technology. Other teams based in the US, Asia, Israel and elsewhere are also developing tests based on this technology.