Unique Testing Method as Sensitive as PCR, But Faster Than LFT

By LabMedica International staff writers
Posted on 08 Aug 2022

Image: The new testing method enables detection at low viral levels (Photo courtesy of Unsplash)

A unique testing method is just as sensitive as both PCR and LAMP tests - currently used in hospital settings - and is also faster and more sensitive than lateral flow tests, enabling detection at low viral levels. Known as Reverse Transcription-Free EXPAR (RTF-EXPAR) testing, this new technology offers detection in as little as 10 minutes.

The testing method invented at the University of Birmingham (Birmingham, UK) is set for a global rollout after its commercial rights were exclusively licensed to the world’s largest COVID-19 test provider, Innova Medical Group, Inc. (Pasadena, CA, USA). The speed of the test is based, in part, on its avoidance of slower, reverse transcriptase-based technologies, and provides the ease of use and speed of lateral flow tests with the sensitivity of PCR testing. Detailed test evaluations reveal the method delivers a fast, accurate, highly sensitive and simple test for COVID-19, meaning the test could be deployed at entertainment venues, airport arrival terminals, and in remote settings where clinical testing laboratories are not available.

The method can be used with testing techniques which bypass the need for laboratory equipment, and this is expected to reduce delays in waiting for test results, which currently require samples to be sent to specialist laboratories. The assay was invented and tested at the University of Birmingham, which found its sensitivity to be equivalent to quantitative PCR testing. The new RTF-EXPAR testing platform is also being adapted for the detection of other viruses, meaning the tests can be quickly adapted to cover both new variants and new viruses. The technology’s new license holder, Innova, is aiming to accelerate RTF-EXPAR’s global rollout for widespread use by 2023.

“The RFT test rapidly amplifies small quantities of viral genetic material, producing a detectable signal within 10 minutes, much faster than PCR or LAMP testing, and even quicker than lateral flow tests,” explained Professor Tim Dafforn from the University of Birmingham. “The reverse transcription and amplification steps slow down existing COVID assays like LAMP and PCR, which are based on nucleic acid detection. An ideal test would have the ‘best of both worlds’ - both sufficiently sensitive and speedy.”

“The new RTF test achieves that goal in two ways. Firstly, the assay team designed a new RNA-to-DNA conversion step that avoids reverse transcription and secondly, the amplification step to generate the read-out signal uses EXPAR, an alternative DNA amplification process,” added Professor Dafforn.

“EXPAR amplifies DNA at a single temperature, thus avoiding lengthy heating and cooling steps found in PCR,” said Professor James Tucker from the University of Birmingham. “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 RTF technology developed at the University of Birmingham hits a testing sweet spot. It’s just as sensitive as PCR and LAMP tests, but without the time constraints and laboratory equipment required for these methods,” said Robert Kasprzak, Chief Executive Officer at Innova.