Dogs’ acute sense of smell can even surpass effectiveness of some clinical laboratory testing in detecting certain diseases in humans
When it comes to COVID-19 testing, a recent Italian study demonstrates that trained dogs can detect SARS-CoV-2 with accuracy comparable to rapid molecular tests used in clinical laboratories. The researchers wanted to determine if dogs could be more effective at screening people for COVID-19 at airports, schools, and other high-traffic environments as a way to detect the coronavirus and reduce the spread of this infectious disease.
Scientists at the State University of Milan in Italy conducted a study that shows dogs can be trained to accurately identify the presence of the COVID-19 infection from both biological samples and by simply smelling an individual.
For their validation study, the Italian team trained three dogs named Nala, Otto, and Helix, “to detect the presence of SARS-CoV-2 in sweat samples from infected people. At the end of the training, the dogs achieved an average sensitivity of 93% and a specificity of 99%, showing a level of accuracy highly consistent with that of the RT-PCR [reverse transcription polymerase chain reaction] used in molecular tests and a moderate to strong reproducibility over time,” Nature reported.
RT-PCR tests are the current gold-standard for SARS-CoV-2 detection. This is yet another example of scientists training dogs to smell a disease with “acceptable” accuracy. This time for COVID-19.
“We only recruited dogs that showed themselves predisposed and positively motivated to carry out this type of activity. One of the fundamental aspects was not to cause stress or anxiety in the subjects used,” Federica Pirrone, PhD (above), Associate Professor, Department of Veterinary Medicine and Animal Sciences, University of Milan, and one of the authors of the study told Lifegate. “Training always takes place using positive reinforcement of a food nature: whether it’s a particularly appetizing morsel, a biscuit, or something that associates the dog’s search with a rewarding prize.” In some instances, dogs have been shown to be as good or more effective at detecting certain diseases than clinical laboratory testing. (Photo copyright: Facebook.)
Dogs More Accurate than Rapid Antigen Testing
Nala and four other dogs (Nim, Hope, Iris and Chaos) were later trained by canine technicians from Medical Detection Dogs Italy (MDDI) to identify the existence of the SARS-CoV-2 virus by directly smelling people waiting in line in pharmacies to get a nasal swab to test for the coronavirus.
Working with their handlers, the five dogs accurately signaled the presence or absence of the virus with 89% sensitivity and 95% specificity. That rate is “well above the minimum required by the WHO [World Health Organization] for rapid swabs for SARS-CoV-2,” according to Nature.
“The results of studies published so far on the accuracy of canine smell in detecting the presence of SARS-CoV-2 in biological samples (e.g., saliva, sweat, urine, trachea-bronchial secretions) from infected people suggest that sniffer dogs might reach percentages of sensitivity and specificity comparable to, or perhaps even higher, than those of RT-PCR,” the scientists wrote in Scientific Reports.
“However, although most of these studies are of good quality, none of them provided scientific validation of canine scent detection, despite this being an important requirement in the chemical analysis practice. Therefore, further applied research in this field is absolutely justified to provide definitive validation of this biodetection method,” the researchers concluded.
Other Studies into Using Dogs for Detecting Disease
Scientists from the Division of Biological and Health Sciences, Department of Agriculture and Livestock at the University of Sonora; and the Canine Training Center Obi-K19, both in Hermosillo, Mexico, conducted the study “as part of a Frontiers of Science Project of the National Council of Science and Technology (CONACYT), in which in addition to analyzing sweat compounds, trained dogs are put to sniff the samples and make detections in people who show symptoms or could be positive for coronavirus,” Mexico Daily Post reported.
The researchers trained four dogs with sweat samples and three dogs with saliva samples of COVID-19 positive patients. The samples were obtained from a health center located in Hermosillo, Sonora, in Mexico. The dogs were restricted to spend five minutes per patient and the researchers calculated the performance of the dogs by measuring sensitivity, specificity, and their 95% confidence intervals (CI).
The researchers concluded that all four of the dogs could detect COVID-19 from either sweat or saliva samples “with sensitivity and specificity rates significantly different from random [sampling] in the field.” According to the Frontiers in Medicine study, the researchers found their results promising because, they said, it is reasonable to expect the detection rate would improve with longer exposure to the samples.
The objective of the Mexican researchers is for the dogs to ultimately reach the sensitivity range requested by WHO for the performance of an antigen test, which is at least 80% sensitivity and 97% specificity. If that goal is achieved, dogs could become important partners in the control of the COVID-19 pandemic, the scientists wrote.
Data obtained so far from these studies indicate that biosensing dogs may represent an effective method of screening for COVID-19 as well as other diseases. More studies and clinical trials are needed before the widespread use of dogs might become feasible. Nevertheless, scientists all over the world are finding that Man’s best friend can be a powerful ally in the fight against the spread of deadly diseases.
In the meantime, the gold standard in COVID-19 testing will continue to be the FDA-cleared assays used by clinical laboratories throughout the United States.
A Penn Medicine news release noted that “The RAPID technology … transforms the binding event between the SARS-CoV-2 viral spike protein and its receptor in the human body, the protein ACE2 (which provides the entry point for the coronavirus to hook into and infect human cells), into an electrical signal that clinicians and technicians can detect. That signal allows the test to discriminate between infected and healthy human samples. The signal can be read through a desktop instrument or a smartphone.”
Though still in its early stages, the technique potentially offers dramatically lower costs and faster results than traditional RT-PCR (reverse transcription polymerase chain reaction) molecular tests. Moreover, the RAPID technology might be useful for identifying other types of biomarkers and could be the basis for diagnostic tests that help reduce the cost-per-test in medical laboratory testing while providing comparable sensitivity and specificity to existing methodologies.
Clinical trials began on January 5, 2021, and the Penn Medicine researchers say the IVD test technology can be applied to other infectious diseases, which, if proven accurate, would be a boon to clinical laboratory testing.
Diagnostic Test Results in Four Minutes for Less than $5/Test
According to the news release, the RAPID 1.0 (Real-time Accurate Portable Impedimetric Detection prototype 1.0) biosensor test costs less than $5 and can deliver results in four minutes. The researchers reported overall accuracy of 87.1% on (139) nasal swab samples and 90% on (50) saliva samples.
The technology uses electrodes that can be mass-produced at low cost on commercially-available screen printers, the researchers said. Results can be read on electronic devices connected to a PC or smartphone.
Does Penn Medicine’s RAPID 1.0 Test Replace Traditional RT-PCR Testing?
In their published study, the Penn Medicine researchers cited the need for “fast, reliable, inexpensive, and scalable point-of-care diagnostics.”
RT-PCR tests, they said, “are limited by their requirement of a large laboratory space, high reagent costs, multistep sample preparation, and the potential for cross-contamination. Moreover, results usually take hours to days to become available.”
Researchers who have studied the SARS-CoV-2 coronavirus know that it uses a spike-like protein to bind to angiotensin-converting enzyme 2 (ACE2) receptors on the surfaces of human cells.
As described in Penn Medicine’s published study, the biosensor contains ACE2 and other biochemical agents anchored to an electrode. When the SARS-CoV-2 coronavirus attaches to the ACE2, the biosensor transforms the chemical reaction into an electrical signal that can be measured on a device known as a potentiostat.
The researchers tested their RAPID 1.0 technology with two commercially available potentiostat models:
The researchers initially developed the electrode as a printed circuit board, which is relatively expensive. To reduce costs, they constructed a version that uses filter paper as the main component. The researchers noted that one screen printer in a lab can produce 35,000 electrodes per day, including time needed to incorporate the chemical elements. “However, it must be noted that these steps can be fully automated into a production line for industrial purposes, drastically reducing time requirements,” they wrote.
The test can be performed at room temperature, they added, and total cost per unit is $4.67. Much of that—$4.50—is for functionalizing the ACE2 recognition agent. The cost for the bare electrode is just seven cents.
“The overall cost of RAPID may be further reduced through recombinant production of ACE2 and ACE2 variants,” the researchers said, adding that the RAPID 1.0 test can detect the SARS-CoV-2 coronavirus at low concentrations correlating to the earliest stages of the COVID-19 disease.
Testing Penn Medicine’s RAPID 1.0 Test
The researchers evaluated the technology in blinded tests with clinical samples from the Hospital of the University of Pennsylvania. The evaluation included 139 nasal swab samples, of which 109 were determined to be COVID-19 positive by RT-PCR tests and clinical assessments. Among these, the RAPID test successfully detected the SARS-CoV-2 coronavirus in 91 samples, for a sensitivity rate of 83.5%. One sample was from a patient diagnosed with the highly contagious SARS-CoV-2 Alpha variant B.1.1.7, which the test correctly identified as positive.
Among the 30 samples determined to be COVID negative, the RAPID test scored a specificity rate of 100%, meaning no false positives. Overall accuracy, including sensitivity and specificity, was 87.1%.
The researchers also analyzed 50 saliva samples: 13 COVID-positive and 37 COVID-negative. The test correctly identified all 13 positive samples but produced five false-positives among the 37 negative samples, for a specificity rate of 86.5%. The researchers speculated that this could be due to interactions between ACE2 and other biomolecules in the saliva but suggested that performance “will improve when using fresh saliva samples at the point-of-care.”
Are There Other Applications for the RAPID Test?
The Penn Medicine news release said the RAPID technology can be adapted to detect other viruses, including those that cause Influenza and sexually-transmitted diseases.
Robert Michel, Editor-in-Chief of Dark Daily and its sister publication The Dark Report, said the test points to one silver lining in the COVID-19 pandemic. “Researchers around the world intensified their work to find ways to identify the SARS-CoV-2 virus that are faster, cheaper, and more accurate than the diagnostic technologies that existed at the time of the outbreak. In this regard, the COVID-19 pandemic may have accelerated the development and refinement of useful diagnostic technologies that will disrupt long-established methods of testing.”
Marcelo Der Torossian Torres, PhD, postdoctoral researcher at Penn Medicine and lead author of the study, said in the news release, “Quick and reliable tests like RAPID allow for high-frequency testing, which can help identify asymptomatic individuals who, once they learn they are infected, will stay home and decrease spread.
“We envision this type of test being able to be used at high-populated locations such as schools, airports, stadiums, companies—or even in one’s own home,” he added.
Clinical laboratory managers may want to stay current on the development and possible commercialization of the RAPID 1.0 (Real-time Accurate Portable Impedimetric Detection prototype 1.0) biosensor test by the research team at Penn Medicine.