Testing protocols for SARS-CoV-2, the virus that causes COVID-19, require collection of samples of nasopharyngeal swab and transport to a laboratory for a multistep process of extracting, isolating and multiplying viral RNA. The attendant need for specialized equipment and relatively time-intensive analysis cycles can be bypassed with a point-of-care assay developed by researchers from University of Illinois, Urbana-Champaign.

A re-engineered reverse transcription loop mediated isothermal amplification (RT-LAMP) isothermal assay platform incorporates a simple-to-use, portable instrument for reading results with a smartphone in 30 minutes. The test bypasses the RNA extraction and purification steps, obviating the need to send samples to a laboratoryThe microfluidic cartridge is inserted into a portable device with a cradle for a smartphone, enabling its camera to read the test results. Source: William P. King et al. for processing.

Comparable results were produced in a comparison of the RT- LAMP assay with the gold standard polymerase chain reaction technique, based on synthetic nasal fluid spiked with the virus and then with clinical samples. The researchers then integrated the new assay with a small 3D-printed microfluidic cartridge offering two input slots for syringes: one for the sample-containing viral transport media and one for the LAMP chemicals. Both react within the cartridge after being simultaneously injected.

The additively manufactured cartridge is inserted into a hand-held portable instrument with a heating chamber which heats the cartridge to 65° C for the duration of the reaction, and then into a smartphone cradle for reading the results. A positive result will emit fluorescent light after about 30 minutes.

This approach could enable the scalable deployment of COVID-19 diagnostics without laboratory-grade infrastructure and resources, especially in settings where diagnosis is required at the point of collection, such as schools, facilities that care for the elderly or disabled or sporting events.

A research paper is published in Proceedings of the National Academy of Sciences.