Sunday, June 26, 2022

Sniffer dogs ‘can detect Covid with similar accuracy to PCR tests’

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Detection dogs can effectively detect coronavirus infections with up to 99 percent accuracy, according to a new study.

The results of the study in Finland suggest that dogs can be trained to detect Covid-19 with an accuracy comparable to that of a standard PCR test within a few weeks.

The team responsible for the remarkable results published in the online journal BMJ Global Healthsaid sniffer dogs could be a valuable tool in the early stages of a pandemic when other detection resources may not yet be available, and help contain an ongoing outbreak.

Dogs possess an exceptionally keen sense of smell and are able to detect an odor in quantities as low as one part per trillion, far exceeding any available mechanical alternative, scientists say.

To test how their skills translate to real-world conditions, the researchers trained four dogs to sniff out SARS-CoV-2 — the virus responsible for Covid — in spring 2020.

The team selected dogs that had previously been trained to sniff out illegal drugs, dangerous goods or cancer.

To test the dogs’ competence, the team collected four skin swab samples from 420 volunteers. Each dog sniffed skin samples from 114 of the volunteers who had tested positive for a PCR swab test and 306 who had tested negative. Samples were presented to each dog at random over 7 experimental sessions.

During training, the dogs were able to detect infections with an accuracy of 92 percent and those without with an accuracy of 91 percent.

The Finnish researchers said only minor variations were found between the dogs – the best performers scored 93 percent for sensitivity and 95 percent for specificity, while the worst performers scored 88 percent and 90 percent in the same categories.

After preliminary testing, the dogs’ detection abilities were used to sniff out 303 arriving passengers at Helsinki-Vantaa International Airport, Finland, between September 2020 and April 2021. Each passenger also underwent a PCR swab test.

Miraculously, the results of the sniffer dogs and the PCR tests matched in 296 out of 303 (98 percent) of the real samples.

The dogs correctly identified the samples as negative in 296 of 300 (99 percent) PCR-negative swab tests and identified three PCR-positive cases as negative, the researchers said.

Due to the low prevalence of the virus among airport passengers (less than 0.5 percent), the dogs were also presented with 155 samples from people who tested positive in a PCR swab test.

They were able to correctly identify almost 99 percent of them as positive. Had these “spike” samples been included in the real study, the researchers said the dogs’ performance would have achieved 97 percent sensitivity and 99 percent specificity.

The study suggests that trained sniffer dogs would save a lot of time and resources, since they can be used “both in locations with high SARS-CoV-2 prevalence, such as hospitals (to screen patients and staff) and in locations with low prevalence can be used. such as airports or ports (for pre-checking of passengers)”.

Another important finding was that the dogs were less successful at correctly identifying the alpha variant because they had been trained to recognize the wild type. But this just goes to show how well dogs can distinguish between different smells, the researchers said.

“This observation is noteworthy as it demonstrates the robust discrimination of sniffer dogs,” says the report.

“The obvious implication is that training patterns should cover all epidemiologically relevant variants.

“Our preliminary observations suggest that dogs primed with a virus type can be retrained to recognize its variants in a matter of hours.”

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