21 June, 2020
Real time reverse transcription–polymerase chain reaction (RT-PCR) is the most widely used method for detecting the kinds of RNA viruses we're dealing with now as part of the COVID-19 pandemic. Unfortunately, as a testing method, it has a number of glaring downsides.
RT-PCR requires highly trained personnel, sophisticated infrastructure, and the transport of samples to central laboratories, not to mention a level of sensitivity and specificity that are hard to deliver, even under the best of circumstances. What is needed, according to KAUST Associate Professor of Bioengineering, Magdy Mahfouz, "is an efficient, rapid, accurate, specific, sensitive, and user-friendly detection method to manage and control the spread of COVID-19."
Mahfouz and his team have developed a solution they are calling iSCAN for in-vitro Specific CRISPR-based Assay for Nucleic acids detection. It's a system that involves Reverse transcription loop-mediated isothermal amplification (RT-LAMP) coupled with CRISPR-Cas12 for the rapid, specific, accurate, sensitive detection of the SARS-CoV-2 virus that is responsible for the current COVID-19 pandemic.
The researchers are currently collaborating with different groups in the Kingdom to benchmark iSCAN against commercial kits including RT-qPCR, the gold standard for SARS-co-V2 detection.
"The current version of iSCAN still needs extensive benchmarking at different testing facilities under field conditions. And several hurdles are still required to obtain the emergency use authorization from the Saudi FDA," Mahfouz said. "But, at this stage, we are very cautiously optimistic."
iScan is designed to be rapid, and specific. Unlike other tests, detection depends on the identification and subsequent cleavage of the SARS-CoV-2 genomic sequences by the Cas12 enzyme, which helps to greatly reduce the incidence of false negatives.
Another key aspect of iSCAN is that it is both field-deployable and easy to use. The equipment needed is minimal and can be transported and stored over long distances, and without specialized equipment.
Best of all the test can be deployed in the hands of untrained people as the colorimetric reaction coupled to lateral flow immunochromatography makes the assay results easy to assess.
Mahfouz and his team feel that the iSCAN approach is suitable for large-scale use now. And with each new wave of the pandemic, a test that is more rapid, accurate, specific, sensitive and user-friendly could help make a big impact. Deployment of iSCAN could allow infected people to be more effectively isolated, and thus to help limit the accelerating spread of the virus.
The iSCAN method has been validated using extracted RNAs from clinical samples from COVID-19 positive patients, which provides the possibility of widespread deployment for virus detection now, before the world sees another massive spike in cases, and subsequent deaths as a result.
"We envision the development of the current version of iSCAN, in the future, to a version that would be as easy to use as a pregnancy test or glucose sensor. Of course none of this would have been possible without the tireless work of my team members including Zahir Ali, Rashid Aman, Ahmed Mahas, Tin Marsic, and Norhan Hassan," Mahfouz said.