Scientists at the Tulane University in the US have developed a Covid-19 test that can be read using a smartphone to aid in widening testing capacity in community settings.

Leveraging the gene-editing technology, CRISPR, the assay can identify very small amounts of SARS-CoV-2 virus RNA in saliva to diagnose Covid-19 in 15 minutes.

Rapid PCR tests need nasal swab samples and are conducted in laboratory settings by trained professionals with the help of sophisticated equipment.

A saliva-based test alleviates the need for lab processing and can potentially increase testing capacity in outpatient clinics, community settings and other sites quickly.

Tulane University School of Medicine Biotechnology Innovation Weatherhead presidential chair Tony Hu said: “This test addresses the critical needs for a rapid, ultrasensitive Covid-19 diagnosis along with effective large-scale screening efforts.

“Our development can quickly identify patients who have the virus, which is required to help address the ongoing threat to public health worldwide.”

Unlike PCR tests, this latest test does not need an RNA isolation step.

For this test, saliva is mixed with an assay solution on an assay chip and heated to amplify a small region of viral RNA.

A modified CRISPR complex that has a guide RNA specific for this virus RNA region rapidly attaches and cleaves both the amplified RNA region and a tagged DNA probe to give a fluorescent signal that can be read using a smartphone device.

The researchers have sought emergency use authorisation (EUA) from the Food and Drug Administration (FDA) for the CRISPR-based approach, which amplifies an assay signal.

This quick, sensitive and user-friendly assay needs minimal steps and less equipment.

Test results can be read by a prototype smartphone-based fluorescent microscope device for point-of-care use.

Last week, UC Berkeley and Gladstone Institutes’ researchers developed a Covid-19 diagnostic test that can provide results in 15 to 30 minutes using a smartphone camera.