New CRISPR-based COVID-19 point-of-care diagnostic

A COVID-19 diagnostic kit is in development that uses CRISPR and can be performed in a single test tube in one hour.

Professor Feng Zhang of the Broad Institute of MIT and Harvard and colleagues developed the diagnostic platform STOP (SHERLOCK Testing in One Pot). This platform advances the CRISPR-based SHERLOCK diagnostic technology (see BioNews 897) so the test can be performed in a single test tube in just one hour, enabling testing closer to point-of-care or at home.

'Since STOPCovid can work in less than an hour and does not require any specialised equipment, and if our preliminary results from testing synthetic virus in saliva bear out in patient samples, it could address the need for scalable testing to reopen our society,' said co-inventor Dr Jonathan Gootenberg.

Professor Zhang previously developed the SHERLOCK CRISPR SARS-CoV-2 test kit which received emergency use authorisation from the US Food and Drug Administration (FDA) last week. However, this test is designed to only be used in certified laboratories.

The reason STOPCovid is more portable is that the amplification of the viral genome and the subsequent detection can be performed at the same temperature, allowing all the chemicals needed to run a test to be contained in a single test tube. As such, the test tubes do not need to be opened to transfer chemicals, decreasing the probability of contamination and unreliability.

STOPCovid can detect small copies of the coronavirus in swab or saliva samples. Initial results indicate that it has 100 percent specificity, meaning it did not detect the coronavirus when not present, and 97 percent sensitivity, meaning it only missed the presence of the coronavirus three percent of the time.

CRISPR is best known for its applications in genome editing, but in SHERLOCK, CRISPR's ability to bind specific DNA sequences is harnessed to detect the RNA of the coronavirus genome in the samples. Once the associated CAS enzyme cuts the viral RNA, a fluorescence signal is generated, which reveals the results on a paper strip, similar to how a pregnancy test displays results.

The inventors are currently in discussion with potential commercial partners to turn the test into a cartridge-like device, similar to a pregnancy test.

'The ability to test for COVID-19 at home, or even in pharmacies or places of employment, could be a game-changer for getting people safely back to work and into their communities,' said Professor Zhang. 'Creating a point-of-care tool is a critically important goal to allow timely decisions for protecting patients and those around them.'

The protocol for STOPCovid has been published as a preprint on medRxiv.