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Point-of-Care Covid-19 Diagnostic Shows High Accuracy

CovidNudge unit

Blue circular CovidNudge cartridge sites inside the NudgeBox analyzer (Thomas Angus, Imperial College London)

18 Sept. 2020. A test for SARS-CoV-2 viruses in humans is shown in field tests to return diagnostic results in 90 minutes with accuracy comparable to the gold-standard RT-PCR test. Results of the CovidNudge tests developed by the company DNANudge in London appear in yesterday’s issue of the journal The Lancet Microbe.

While turnaround times for Covid-19 tests at central laboratories in the U.S. are now down to about two days, health care facilities still need their own molecular diagnostics for patients with comparable result quality, but in a much faster time. To fill that need, DNANudge, a spin-off enterprise from Imperial College London offers its CovidNudge test, a self-contained testing system with cartridges for depositing nasal sample swabs and analyzing deposited genetic material in the swab for signs of SARS-CoV-2 viruses responsible for Covid-19 infection.

Deep nasal swab samples, taken from the back of the throat, are inserted into the sample collection cartridge, the blue unit in the photo. There, RNA is separated from the sample and amplified, then analyzed with reverse transcription-polymerase chain reaction, or RT-PCR within the unit. RT-PCR analysis, the so-called gold standard for molecular testing, usually requires a remote lab, but in this case, microfluidics, or lab-on-a-chip components in the larger NudgeBox perform the analysis on the spot. The WiFi-enabled CovidNudge transmits its data to a cloud-based analytical program. Results showing the absence or presence of the virus, negative or positive, are returned, according to the company within 90 minutes, to designated recipients, including the patient’s phone.

A team from Imperial College led by Graham Cooke, professor of infectious diseases, took 386 paired-sample nasal swabs in April and May 2020, when the U.K. experienced a higher infection rate than today. Participants, who agreed to give two nasal swabs, consisted mainly of health care workers serving Covid-19 patients (73% of participants), but also emergency room and admitted patients, at three London hospitals. The paired samples were sent to a remote lab for standard RT-PCR analysis or assessed in a CovidNudge unit.

The results show the CovidNudge results for emergency room and admitted hospital patients matched 100 percent with RT-PCR lab analysis. Among health care workers, 93 percent of CovidNudge samples matched in accuracy with their RT-PCR samples, with an overall true-positive sensitivity of 94 percent. Across all participants, true-negative specificity was 100 percent. Some 18 percent of participants overall were found with SARS-CoV-2 viruses, 67 in the CovidNudge group and 71 among the RT-PCR participants.

“These results suggest the test, which can be performed at a patient’s bedside without the need to handle any sample material, has comparable accuracy to standard laboratory testing,” says Cooke in an Imperial College statement. “Many tests involve a trade-off between speed and accuracy, but this test manages to achieve both.”

Biomedical engineering professor Chris Toumazou who co-founded DNANudge, believes the CovidNudge test has uses beyond health care facilities. “The platform is well suited to testing in primary care and community settings,” notes Toumazou, “with potential for use in non-health care settings such as care homes, schools, transport hubs, offices, and, to help bring the arts back, in theaters and venues. However, further studies of real-world effectiveness in non-clinical settings would be required prior to widespread deployment.”

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