Rapid SARS-CoV-2 Microchip-Based Test Using RT-PCR Validated

Coronavirus particles, illustration - SARS-CoV-2 virus
Credit: KATERYNA KON/SCIENCE PHOTO LIBRARY/Getty Images

Researchers have developed a microchip-based real-time PCR test that they report provides accurate results much faster than standard testing and requires 10 times less reagents than the tube-based RT-PCR tests currently considered the standard. This new test, they suggest, could kickstart testing expansion, since supplies of current testing kits and reagents have been limited, and it could be deployed in remote locations, including clinics and airports, due to its ease of use and portability.

The study was conducted by researchers at Simon Fraser University, BC, Canada, and results were published last week in The Journal of Molecular Diagnostics.

“This research offers a cheaper, faster alternative to the most reliable and sensitive test currently used worldwide, without sacrificing sensitivity and reproducibility,” says molecular biology and biochemistry professor Peter Unrau, who led the team.

Unrau, along with Ph.D. candidate Razvan Cojocaru and Master’s student Iqra Yaseen, first evaluated test sensitivity in the lab.

“The microchip kit miniaturizes the reaction volumes by 10-fold, resulting in lower reagent consumption and faster assay times (as low as 30 minutes vs approximately 70 minutes), while maintaining the same gold standard in sensitivity as the higher-volume techniques,” they reported.

They write that testing accuracy was partially dependent on how the patient samples were collected, with sputum being the most accurate, followed by NP swabs and saliva, and lastly oropharyngeal swabs. Further, they found that NP swabs may increase the viral exposure of health care worker if insufficient personal protective equipment is available, increasing the risk of transmission.

The test kit was next sent to a clinical team at St. Paul’s Hospital in Vancouver, British Columbia, to determine its ability to detect COVID-19 in patient samples. The microchip PCR COVID-19 test kit results aligned with hospital testing results, which supported its effectiveness.

Because the kit comes preloaded with SARS-CoV-2 primers and probes, the researchers suggest it may reduce operator-associated errors, improving the reliability of analysis in remote settings. According to their study, the assay reliably has a limit of detection of approximately 1 viral copy per reaction, with mean Ct values that correlate with dilutions that range from approximately 1500 to 1 expected copies per reaction: The assay shows comparable accuracy to that of a clinically validated RT-qPCR assay for the tested 21 COVID-19 NP patient samples.

As they note, the current COVID-19 RT-qPCR test detects the virus by single-plex amplification of one or two segments of the NORF1bE, or RdRp genes, whereas other assays have been developed to take advantage of multiplex amplification, amplifying multiple genes in a single reaction.  Regardless of the method, amid the pandemic, most of these assays require supply-limited reagents in high volumes and significant technical labor for preparing complex reagent mixtures, resulting in high-cost assays with potential for human error.

Microchip real-time PCR has been proven to be a user-friendly technology that can provide reliable, sensitive, and specific results in less time. These advantages are attributed to the miniaturized reaction volumes, where the chip’s high surface area to volume ratio offers high heat transfer efficiency.

The COVID-19 detection kits developed by Lumex Instruments Canada and validated by Unrau’s team are low power (100 watt), compact, lightweight and available internationally.

Supply chain shortages of reagents and test kits during the pandemic has slowed the rapid expansion of clinical testing. This new COVID-19 test kit is another tool in the toolbox that uses less of the supply constrained reagents to achieve fast and accurate results.

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