A rapid, saliva-based test for COVID-19 could enable testing, diagnosis, and prescribing to take place in a single office visit by immediately confirming whether a patient has the infection and needs to be treated, researchers say. The test has sparked commercial interest and earned additional funding from the Canadian government.
The test uses a DNA aptamer – a short, synthetic oligonucleotide that binds to a specific molecular target – that shows high affinity for the SARS-CoV-2 spike protein and its variants. The approach “can be rapidly adapted to different threats,” as well, Leyla Soleymani, PhD, an associate professor of engineering physics at McMaster University, Hamilton, Ontario, Canada, told this news organization. Her team invented the approach.
Adaptable to other pathogens
Current gold-standard COVID-19 tests are based on reverse transcription-polymerase chain reaction (RT-PCR), which are sensitive but costly, complicated, and require waiting at least a couple of days for results, according to Dr. Soleymani and colleagues. Rapid nucleic acid and antigen tests have only “moderate” sensitivity and specificity, particularly when viral loads are low. None have been shown to work well with saliva samples.
By contrast, the new test “uses a reader and test cartridges, similar to the glucose reader,” said Dr. Soleymani, who is also Canada Research chair in Miniaturized Biomedical Devices. A small sample of saliva is added to a chemical reagent and inserted into the reader, which is attached to a smartphone. Once commercialized, the point-of-care test is expected to be performed quickly in a physician’s office or in a clinic.
“The same reader can be applied to a variety of infectious diseases or infection panels by developing new cartridges,” Dr. Soleymani explained. “Noroviruses and bacteria such as C. difficile are on our list” to examine next.What’s more, she added, “this test is ideally positioned for settings where access to centralized labs is not possible, such as less developed countries.”
The team’s recent studies seem to support the promise. A study published last year in the international edition of Angewandte Chemie documents the development of the test, which at that point could detect wild-type SARS-CoV-2 and its Alpha and Delta variants in unprocessed saliva samples in 10 minutes with 80.5% sensitivity and 100% specificity.
This study was followed in January 2022 by a paper in Chemistry showing that the device also detected Alpha, Gamma, Epsilon, Kappa, and Omicron variants, demonstrating its potential for recognizing rapidly evolving targets such as those found in SARS-CoV-2.
In another demonstration of its versatility, the technology was recently adapted and successfully detected animal viruses from saliva samples.
Commercial and government funding
The findings prompted Zentek, an intellectual property development and commercialization company in Guelph, Ont., to license the technology, with plans to invest more than $1 million in the next 5 years to scale up production of the test components and adapt the technology for other forms of infection.
Furthermore, the collaborative efforts required to develop the test and move it forward gained funding from Canada’s Natural Sciences and Engineering Research Council, which is investing nearly $1.5 million in the form of two grants: $1 million to further streamline the technology development in preparation for the next pandemic and $488,440 (including $140,000 from Zentek) to get the current test to market as quickly as possible.
Meanwhile, Dr. Soleymani is urging clinicians “to be open to nontraditional diagnostic approaches even if the traditional tests do the job. Such tests are more rapid and can be used to enable personalized medicine. Our success relies on collaboration and support from clinicians.”
Further validation needed
Daniel Kuritzkes, MD, chief of infectious diseases at Brigham and Women’s Hospital and the Harriet Ryan Albee Professor of Medicine at Harvard Medical School, Boston, commented on the study in response to a request from this news organization.
While “it’s always good to have more testing options available,” he said, “we don’t yet have very much information about performance characteristics of the test – that is, its sensitivity and specificity. I’d like to see the performance characteristics of this test compared to PCR tests and to the current rapid antigen tests using a large number of patient samples with currently circulating variants, and tests over time to see how soon tests become positive after symptom onset and for how long they remain positive.”
“Further validation studies and emergency use authorization or approval by regulatory authorities are needed before we will see this test implemented in the field,” Dr. Kuritzkes concluded.
A version of this article first appeared on Medscape.com.