- Researchers have found that an unusual coronavirus diagnostic tool picks up the virus days before the standard PCR tests can identify it.
- Dogs trained to detect the particular scent of COVID-19 patients can correctly identify infected people early, and they don’t make mistakes, according to new reports.
- A PCR test might return a false-negative result if taken in the first days after exposure to the virus, but researchers say the dogs do not have the same problems.
The last time we reported on very good boys ET, Kossi, Miina, and Valo, we had learned they all got jobs at the Helsinki airport running COVID-19 screenings for incoming passengers. They would work in shifts of two, and they’d sniff out the coronavirus in people. ET, Kossi, Miina, and Valo are four dogs trained to detect a particular odor from coronavirus patients.
Doctors from various countries started training dogs to detect the smell of COVID-19 patients several months ago, and the results are starting to come in. The Finnish researchers have realized that the dogs have a huge advantage over regular PCR tests, as they can detect the illness well before the traditional tests pick up the virus.
A report from The Times explains that the researchers were initially puzzled by the COVID-19-sniffing dogs. The animals were identifying passengers at the airport who had the disease. When tested with regular PCR machines, the results were coming up negative. It appeared initially that the dogs were giving false-positive results.
A few days later, the people who tested negative started getting symptoms proving that the dogs were right. What the animals did was to detect the virus even before a PCR test would pick it up.
“They’re actually finding PCR negatives that are going to be PCR positives in a week’s time,” Dr. Anna Hielm-Björkman said, adding that other researchers in countries using dogs for COVID-19 screening have observed the same behavior. “It’s kind of a problem when you have a test that is so much better than the gold standard because you cannot validate it in any normal way.”
“PCRs are around 70 percent,” the researcher said of false-negative results. “The good dogs never go under 100 percent.”
If taking a COVID-19 test too early after exposure to the virus, there’s a high chance the result will be negative. The virus needs a few days to start multiplying before the test can return a positive result. Patients are actually infectious a few days before the onset of symptoms, at which point they would likely test positive for the virus. If infectious, a patient ejects viral particles when talking, coughing, or sneezing. The same particles would end up on nasal swabs.
A previous report explained that the dogs don’t actually get in contact with passengers for safety reasons. They’re given a wipe that passengers used on their skin. The wipe is placed in a container, as shown in the image above, next to three other samples. The dog will then indicate a positive sample by “yelping, pawing, or lying down.”
Having dogs catch COVID-19 patients before the PCR would be a great tool for screening purposes. The animals could be used in crowded places like airports to identify potential asymptomatic spreaders quickly. The problem with this resource is that it’s not exactly scalable. Dogs need to be trained to detect the smell, and they need to be protected. There have been cases where dogs caught COVID-19 from their masters.
However, the research does make a great point that COVID-19 could be diagnosed earlier than current PCR tests can. It’s unclear how the PCR tests could be improved to provide results even faster.