As you know, current COVID-19 tests only give results after 30 minutes. But researchers at the University of Birmingham have just invented an efficient process capable of giving precise results in less than five minutes.
This technique combines the ease of use and speed of lateral flow testing with the inherent sensitivity of an RNA test. It contains reagents which can be used in existing tests and meets current needs in terms of tests for the detection of the virus or its variants.
The speed and sensitivity of this method was demonstrated in a recent pending review article published on MedRxiv. The researchers used samples from patients, provided by Public Health England, as part of their research.
The Reverse Transcriptase Free EXPAR test (RTF-EXPAR)
The proposed test is based on a reverse transcription polymerase chain reaction (RT-PCR). The first step uses a reverse transcriptase enzyme to convert RNA into DNA while the second requires cycles of heating and cooling to amplify the copied DNA to detectable levels using a DNA polymerase enzyme.
RTF-EXPAR converts viral RNA into DNA in a single step. It was combined with a technique called the Exponential Amplification Reaction (EXPAR) to increase DNA concentration to detectable levels at a constant temperature.
Reducing the operation to less than 20 minutes has proven difficult, but with technological advances, single temperature processes have been developed. This helped to reduce the time required for the operation.
A patent application covering the method and its use in diagnostic equipment (the famous test) has been filed by a consortium from the University of Birmingham, as well as a license for the rapid production of this test.
The RTF-EXPAR test: how does it work?
This test therefore contains a binding DNA sequence, which after having recognized the viral RNA of SARS-CoV-2 binds to it. An enzyme (BstNI), in the presence of the viral RNA, will cut a short section of the binding DNA after recognizing it. This will allow free viral RNA to bind to more binding DNA. The cycle will repeat itself and will make it possible to detect whether there is a positive case.
This approach has been tested by researchers who incubated samples of BstNI, DNA binding and SARS-CoV-2 introduced into EXPAR reagents at a constant temperature of 50 ° C.
Detection possible in less than 5 minutes
Positive test results were obtained within plus or minus 4.72 minutes with no signal for the control sample after 10 minutes of incubation. A SARS-CoV-2 RNA concentration of approximately 72.7 copies / µL was detected in the positive sample, a value approximately 10 times lower than the average viral load observed in samples from COVID-19 patients . Which says a lot about the efficiency of the process.
For clarification, beyond SARS-CoV-2, the use of the RTF-EXPAR method can be extended to the detection of any RNA-based infectious agent or any disease biomarker, depending on the researchers.