A simplified point-of-care assay that turns a smartphone into a fluorescence microscope could expand coronavirus disease 2019 (COVID-19) testing capability, researchers reported in a study in Cell.
The assay, which uses clustered regularly interspaced short palindromic repeats (CRISPR) gene editing technology, emits a fluorescent signal in the presence of the novel coronavirus’s RNA. A smartphone camera can detect this signal directly, without amplification of the viral genome used in most genetic tests. This means the test can quantify the amount of virus in the sample—the quicker the signal is picked up, the higher the viral load.
In the study, the assay was able to detect RNA extracted from patients’ nasal swabs within 5 minutes. Samples with less virus could be detected within 30 minutes. “Monitoring viral loads quantitatively would allow estimation of infection stage and help predict infectivity, recovery, and return from quarantine in real time,” the authors wrote.
“We plan on applying for [Emergency Use Authorization] in the next few months,” researcher Melanie Ott, MD, PhD, of the Gladstone Institute of Virology at the University of California, San Francisco, wrote in a January email. A rollout in pharmacies and drop-in clinics is planned first, with an at-home test potentially to follow later. The technique targets different parts of the virus’ genome, which should make it less vulnerable to false-negatives as the pathogen continues to mutate.
For now, the test still requires laboratory equipment and RNA extraction. “In the future, our next assay will cut out the need for laboratory in a single-step assay,” Ott wrote. The research team also includes Jennifer Doudna, PhD, who shares a Nobel Prize in chemistry for developing CRISPR-based gene editing.