COVID Testing in Less than 5 Minutes Using Novel RTF-EXPAR Method


Controlling the rate of COVID-19 spread requires an accurate and a faster virus testing strategy. RT-PCR (reverse transcriptase polymerase chain reaction), the most accurate testing method being currently employed is a two-step test that takes around 60 minutes per sample.  

COVID-19 testing

The researchers from the University of Birmingham have reported a novel method for detection of SARS-CoV-2. This could enable much faster testing and is sufficiently sensitive.  

The viral RNA detection by RT-PCR (reverse transcriptase polymerase chain reaction) involves conversion of viral RNA to complementary DNA (cDNA) followed by amplification of cDNA by a quantitative PCR (qPCR). The cDNA is then detected using a fluorescent dye. This takes up to an hour. 


The assay time is considerably reduced from about an hour to few minutes by the newly reported RTF-EXPAR method which uses reverse transcriptase-free (RTF) approach for conversion of RNA into DNA followed by EXPAR (Exponential Amplification Reaction) for amplification at single temperature. The amplification taking place at a single temperature is the key to speed, because it avoids lengthy heating and cooling steps of RT-PCR. Further, the section of DNA being amplified is smaller compared RT-PCR. Hence, EXPAR generates up to 108 strands of DNA product in few minutes. The duplex formation is monitored, as in RT-PCR method using fluorescent dye, SYBR Green.  

Interestingly, the new method can be modified to detect several other infectious diseases caused by RNA viruses, for example Ebola, RSV, etc.  


Carter et al (2020).  Sub-5-minute Detection of SARS-CoV-2 RNA using a Reverse Transcriptase-Free Exponential Amplification Reaction, RTF-EXPAR. Preprint. Published at medRxiv Posted January 04, 2021. DOI: