It seemed like such a great idea. But at the end of the day, as they say, those dogs didn’t hunt. Or at least not well enough.
New research from Toronto throws into question the notion that canines could be used in hospitals to detect patients with a debilitating and highly contagious form of diarrhea caused by the bacterium Clostridium difficile, or C. diff.
Earlier infection control teams in the Netherlands and Vancouver, Canada, had reported success in using dogs to sniff out patients with C. difficile from those with other types of diarrhea, or to find the bacterium’s hard-to-eradicate spores in hospital rooms being cleaned after housing a C. diff patient. In each case, the journal reports were based on the performance of a single trained dog.
But the new research revealed problems when the detective powers of two dogs were compared. To put it succinctly, Chase, a border collie, and Piper, a German shepherd, didn’t agree enough of the time for the researchers to feel confident the dogs were reliable enough to use in the hospital.
“They weren’t always wrong the same way and they weren’t always right the same way. And when I see that variability as a researcher or even as a clinician, it scares me as far as generalizability moving forward,” said Dr. Jeff Powis, medical director of infection prevention and control at Toronto’s Michael Garron Hospital, and senior author of the paper.
“If they could tell somebody had C. diff without an actual stool specimen, that would have saved us an enormous amount of time,” said Powis, who had been excited about the potential of using dogs to detect C. diff. But the study’s findings, published this week in the journal Open Forum Infectious Diseases, has led Powis and his team to conclude canine C. diff detectives aren’t the answer.
“From our assessment, we’re stopping here,” he said.
Diarrhea can be caused by a multitude of pathogens — both bacterial and viral — as well as diet and even a reaction to some medications. But C. diff diarrhea is a particular concern in hospitals because of its potential to spread from patient to patient. Incoming patients who are suspected of having C. diff are typically put in isolation, with hospital staff required to don gowns and gloves every time they enter the room, said Maureen Taylor, a physician assistant on Powis’ team who led the study.
There is no point-of-care test that will rapidly allow hospital staff to rule C. diff in or out, and it takes a day or two to get test results from the laboratory. Getting a diarrhea specimen to send off to the lab for testing can take as long. “Nobody is anxious to take on that job,” Taylor said.
Vancouver General Hospital and VU University Medical Center in Amsterdam had each trained a single dog — a beagle named Angus at the former and a springer spaniel named Cliff at the latter — to detect C. diff, showing some impressive results they had published in medical journals.
But while those studies suggested that the famed olfactory powers of dogs — already used to detect illicit drugs, bombs, and even bedbugs — could be useful, research based on a single dog can’t answer the question of how reliable dogs are at this work in general.
The Michael Garron Hospital team worked with an animal specialist who found and trained Chase and Piper, using metal scent boxes that contained sponges on which stool had been applied. Some of the stool samples were from patients who had C. diff diarrhea. The dogs were given a reward when they successfully found the scent boxes that contained samples contaminated with C. diff.
The work was done in a decommissioned ward, to acclimatize the dogs to a hospital environment.
After extended training came the study. While the dogs were reasonably good at finding C. diff specimens and ignoring specimens that didn’t contain the bacteria, they were occasionally wrong — missing some samples that contained C. diff and mistaking some negative samples as positive. More problematic, though, was that they didn’t make the same mistakes. If they’d both missed specimen 12, for instance, it might mean the concentration of C. diff spores in the stool sample was too low. But that was not the case.
And Chase, who had been at the work longer and had been quite accurate in training, underwhelmed.
“We were impressed at first with Chase. [But] by the time the study actually happened two years later and Piper came on, Chase did not perform in the study as well as Piper did,” Taylor said. She added: “I don’t know dogs very well, but I got the sense by the time we did the study Chase was kind of saying to us: ‘You know what? I’ve moved on.’”
There was also the issue of distractions.
“If there was a breakfast tray on that patient’s bed, [Chase] was way more interested in the breakfast tray than he was in trying to find C. difficile spores,” Taylor noted. Another problem: “The dogs found it hard to pass a toilet without drinking out of it.”
“I don’t know dogs very well, but I got the sense by the time we did the study Chase was kind of saying to us: ‘You know what? I’ve moved on.’”
Maureen Taylor, physician assistant on Powis’ team who led the study
Dr. Marije Bomers, the lead author of the Dutch study, said the Toronto research shows that some dogs are better at this work than others.
“This of course does not mean dogs in general are unable to detect C. difficile at the bedside,” she said, noting Cliff, the spaniel her group used, was very accurate.
But variability in the performances of individual dogs could make it difficult to organize a program of this type, acknowledged Bomers, an infectious diseases specialist. “This study further illustrates that the capability of one dog cannot simply be extrapolated to other dogs, complicating practical implementation of C. diff sniffer dogs on a larger scale.”
VU Medical Center encountered a different problem with its program — the hospital doesn’t have enough C. diff cases to make the dog program cost-effective, Bomers said.
Cliff, the Dutch C. diff sniffer dog, has been retired.
So have Chase and Piper, both rescue dogs. For Chase, all that work learning to detect C. difficile samples hasn’t gone unrewarded. He’s been adopted, Taylor said, by one of the hospital’s pharmacists.