Alternative amplification technique could accelerate COVID-19 testing

An alternative amplification technique to detect SARS-CoV-2 RNA could offer a way to rapidly test large numbers of people for COVID-19, although the technique is not as sensitive as quantitative RT-PCR, the current standard method for COVID-19 testing.

Faster and less complicated testing could aid in the rapid isolation of infected people and could help to identify and prevent new outbreaks of the disease until a vaccine becomes available. Quantitative RT-PCR can successfully detect viral RNA but requires expensive machinery and chemical reagents that can sometimes be in short supply. The standard method also depends on time-consuming temperature cycling steps to amplify enough RNA from a patient sample for detection, resulting in a processing time between 3 and 24 hours in most clinical laboratories.

Viet Loan Dao Thi and colleagues instead propose using a technique called reverse transcription loop-mediated isothermal amplification (RT-LAMP), which can be carried out at a constant temperature using simple equipment and a different set of reagents. In their tests of RNA isolated from 768 nasopharyngeal swabs from individuals tested for COVID-19, Dao Thi et al. determined that RT-LAMP was less sensitive than quantitative RT-PCR but could be used to evaluate large groups of people, with an average test processing times of 30 minutes.

The researchers concluded that RT-LAMP works best for identifying people with moderate to high amounts of SARS-CoV-2 virus in their bodies, but is not sensitive enough to identify infection in people with a low viral load - such as those at the beginning or end of the illness. The researchers also tested the possibility of using RT-LAMP directly on nasopharyngeal swabs - without the need for RNA isolation - but concluded this technique was less sensitive than using isolated RNA.