Harnessing recombinase polymerase amplification for rapid detection of SARS-CoV-2 in resource-limited settings

Cherkaoui, D.; Huang, D.; Miller, B.; McKendry, R. A.

The COVID-19 pandemic has challenged testing capacity worldwide. The mass testing needed to stop the spread of the virus requires new molecular diagnostic tests that are faster and with reduced equipment requirement, but as sensitive as the current gold standard protocols based on polymerase chain reaction. We developed a fast (25-35 minutes) molecular test using reverse transcription recombinase polymerase amplification for simultaneous detection of two conserved regions of the virus, targeting the E and RdRP genes. The diagnostic platform offers two complementary detection methods: real-time fluorescence or visual dipstick. The analytical sensitivity of the test by real-time fluorescence was 9.5 (95% CI: 7.0-18) RNA copies per reaction for the E gene and 17 (95% CI: 11-93) RNA copies per reaction for the RdRP gene. The analytical sensitivity for the dipstick readout was 130 (95% CI: 82-500) RNA copies per reaction. The assay showed high specificity with both detection methods when tested against common seasonal coronaviruses, SARS-CoV and MERS-CoV model samples. The dipstick readout demonstrated potential for point-of-care testing, with simple or equipment-free incubation methods and a user-friendly prototype smartphone application was proposed with data capture and connectivity. This ultrasensitive molecular test offers valuable advantages with a swift time-to-result and it requires minimal laboratory equipment compared to current gold standard assays. These features render this diagnostic platform more suitable for decentralised molecular testing.