The speed and accuracy of a new highly sensitive testing method for COVID-19 that can be deployed at entertainment venues and airport terminals has been confirmed by scientists.
University of Birmingham researchers used a three way comparison study to confirm that the Exponential Amplification Reaction (EXPAR) COVID test is just as sensitive, but faster, than both PCR and LAMP tests which are currently used in hospital settings.
The test, called RTF-EXPAR, gives a sample-to-signal time of under 10 minutes, even for low viral levels where current lateral flow tests are less effective.
Both PCR and LAMP tests detect viral RNA, which can be present in extremely low levels in swabs taken from the mouth and nose. These tests use a two-step process which involves first converting to RNA to DNA (a process called reverse transcription) and then ‘amplifying’ the material many times over so it can be detected in the sample.
Professors Tim Dafforn from Birmingham’s bioscience school said: “Both the reverse transcription and amplification steps slow down existing COVID assays that are based on nucleic acid detection, compared to antigen tests, such as lateral flow, which do not have these steps.
“However, while this makes lateral flow tests faster than those based on PCR and LAMP, in return they are typically less sensitive. An ideal test would be one that is both sufficiently sensitive and speedy – our test, called RTF-EXPAR, achieves this goal.”
RTF-EXPAR achieves this feat in two ways – firstly the assay team designed a new RNA-to-DNA conversion step that avoids reverse transcription, making it reverse transcription-free (RTF).
Secondly their amplification step to generate the read-out signal uses EXPAR, an alternative DNA amplification process to PCR and LAMP.
Professor Dafforn added: “EXPAR amplifies DNA at a single temperature, thus avoiding lengthy heating and cooling steps found in PCR.
“However, while LAMP also uses a single temperature for amplification, EXPAR is a simpler and a more direct process, in which much smaller strands are amplified. This makes EXPAR an even faster DNA amplification technique than not only PCR but also LAMP.”
The study revealed that the RTF-EXPAR method converts under 10 strands of RNA into billions of copies of DNA in under 10 minutes, using a one-pot assay that is compatible with more basic, benchtop equipment than that used with current testing methods.
The assay has been tested at the Surgical Research Laboratory at the University of Birmingham.
The university team is now seeking commercial partners for rapid licensing, to make the RTF-EXPAR test as available as widely as possible.
