February 17, 2022 | Schools, airports, and other venues where large numbers of people congregate could start using a new smartphone-based diagnostic platform that rapidly and inexpensively tests for both COVID-19 and the flu from a small volume of saliva. The technology was originally developed to detect urinary tract infections (UTIs), a prognosticator for sepsis, according to Douglas Heithoff, Ph.D., senior scientist with the Institute for Collaborative Biotechnologies at the University of California, Santa Barbara.
A smartphone app, a smartphone, and a lab kit (from materials priced at around $100) comprise the loop-mediated isothermal amplification (LAMP) assay. “The app is free and accessible,” says Heithoff. “Once you have the kit materials and access to the software, it’s something that could be reused and repeated as a test.”
The cost per test is only $7, he says, which comes from the expendable reagents needed to carry out the chemical reaction, notably the component enzymes. But that should be a reducible expense moving forward if the enzymes are purified in bulk and could help ensure access to all parts of the world.
Up to 96 tests can be done simultaneously, with results produced in 25 minutes, which represents an “incredible advance” in the field, he notes. The technology matches the sensitivity of the Centers for Disease Control and Prevention gold standard PCR test but at a significantly more affordable price point—an important consideration if fair and equal access to precision diagnostic medicine is to extend to low- and middle- income countries.
The custom-built app was developed for the Android operating system and can be downloaded and installed from the Google Play Store, says Heithoff. Users have the option of watching a step-by-step tutorial prior to running test samples.
A study featuring the smartphone-based LAMP assay was published in JAMA Network Open (DOI: 10.1001/jamanetworkopen.2021.45669). Nearly half the world’s population has a smartphone and Android use globally is dominant to that of Apple iPhones, Heithoff says. The Samsung Galaxy S9, on which the dual testing platform was studied, can be purchased for under $200.
Most existing smartphone-based diagnostic kits require additional mechanical components such as cartridges and special monitoring equipment, he adds. This is believed to be the first point-of-care assay for detecting COVID-19 using only a smartphone to gather and quantitatively interpret the data.
The smartphone-based LAMP assay does not have Emergency Use Authorization from the U.S. Food and Drug Administration (FDA) but was developed following conditions that the FDA would ultimately require for an approval, says Heithoff. It is in any case a “very safe” diagnostic since the testing process involves self-collection of a saliva sample, which is all that would be potentially infectious.
As a starting point for the development of the test, researchers first had to contend with the propensity for primer-dimer self-amplification owing to the requirement of six primers per target gene that could potentially increase the incidence of false positives. “We put a lot of effort into working out the protocol and all the conditions and reagents needed to eliminate the occurrence of these primer-dimers,” Heithoff says. Once that was done for the SARS-CoV-2, the same protocols worked “right away” when applied to influenza A and B viruses.
In the cohort study of saliva samples from 50 community-based patients, the novel diagnostic performed on par with PCR tests in detecting SARS-CoV-2 infection. This suggests it could serve as an additional tool to detect COVID-19 that can be readily modified in response to emerging variants as well as other pathogens with pandemic potential.
“The adaptability comes from the design of the specific primers that detect the pathogen’s nucleic acid… it is the only thing that would need to be altered,” says Heithoff. Primer design is a straightforward process based on knowing the genomic sequence of a pathogen.
The LAMP assay detection system consists of a hot plate, cardboard box, and LED lights. The hotplate ensures a consistent 70 degrees Celsius temperature at which the chemical reactions run in a 96-well plate, he explains. A cardboard box creates a dark environment—except for the LED lights, which serve to monitor the reaction.
The smartphone sits atop the box with the camera fitting over a small hole, visually capturing the reaction fluorescence that is occurring over time, Heithoff continues. Blue LED lights shining on the reactions create the images captured by the smartphone camera.
A few years ago, a proof-of-principle for the platform technology was published where UTI-causing pathogens were the detection targets (DOI: 10.1016/j.ebiom.2018.09.001). “That was the first example of human patient samples being measured for pathogens by a [smartphone-based] stand-alone device,” he says.
Motivating development of the assay was a desire to add to the toolkit for fighting the current pandemic domestically and globally, says Heithoff. The research team expects to secure additional grant funding to further develop the test.
It has yet to be determined who would produce the diagnostic kits, but the UCSB team expects to be involved either directly or indirectly as consultants, Heithoff says. To aid the use of the assay as a standalone field test anywhere by anyone with a smartphone, the kits are of simple construction using inexpensive materials.
Further out, the assay could be developed into a home-based test inclusive of all required materials and reagents, Heithoff says. As would be the case in lower income nations lacking some of the needed tools, “you’d have to assemble everything as a single kit with a very simple set of instructions ready to go.”
The rapid UTI urine test remains a lab test and hasn’t undergone further development, Heithoff adds, but “as it stands it is suitable for a clinical environment.” Detecting bacterial infections in the blood with this technology has not yet been done.
For both the UTI and dual COVID/influenza kits, UCSB researchers have been collaborating with doctors at Santa Barbara Cottage Hospital. The core investigative team on the academic side has worked together for years now, he says.