December 14, 2012
Detection Dog Sniffs Out Hospital Infection With High Rate Of Accuracy
[Watch Video: Using Dogs To Sniff Out A Diagnosis]
Lawrence LeBlond for redOrbit.com - Your Universe OnlineHumans have relied on dogs for millennia. Since first being domesticated some 15,000 years ago, dogs have been “man´s best friend” through thick and thin. We have used dogs for work, for sport and for play. They have provided invaluable services to mankind, providing their unique skills as police dogs, seeing-eye dogs, and perhaps their greatest attribute as hunting dogs.
Dogs have played just as an important role in the medical field, being trained as medical response dogs, not only to guide the blind, but also to detect personal medical emergencies before they occur. Many dogs can be trained to hone in their ability to detect an imminent epileptic attack or to alert their diabetic masters of dangerously high or low blood sugar levels.
For the most part, dogs trained in such fields rely on one keen sense to assess the situation: smell. A dog´s sense of smell is much greater than a human´s. This is because its olfactory bulb is forty times bigger than a human´s. A bigger olfactory bulb means more smelling power, and a typical dog has more than a hundred thousand times greater sense of smell than a human.
And it is this sense of smell that attributes to a dog´s ability to sniff out a particular infective component that causes many hospital acquired infections.
A new study, published in the British Medical Journal (BMJ), has found that dogs can sniff out Clostridium difficile with significant accuracy in samples of feces as well as in the air around patients in the hospital. Using a detection dog, researchers were easily able to identify sick patients, based on the dog´s keen sense of smell.
Earlier studies have established that detection dogs can detect certain types of cancers, which are verified by the new findings, implying promising potential for hospitals to better screen patients to prevent C. difficile outbreaks.
C. difficile most commonly affects older people who have recently had antibiotic treatment in the hospital, but it can also start in the community, especially in nursing homes and rehabilitation facilities. Symptoms of C. difficile range from mild diarrhea to life-threatening bowel inflammation.
Such is why early detection is vital to prevent transmission, as well as treat patients who have the infection. Current methods to diagnose C. difficile can be quite expensive and take time, which can delay treatment for up to a week or longer. So for dogs to be able to detect the component, it could save a lot of headaches down the road.
Diarrhea due to C. difficile has a distinct smell, and since dogs have a highly superior sense of smell, researchers from the Netherlands decided to investigate to see whether a dog could be trained to detect that unique odor.
The researchers, from VU University Medical Centre in Amsterdam, turned to a two-year-old beagle called Cliff, which was new to the detection game, for their research. Cliff was trained to detect the component in stool samples as well as in patients with the infection. He was trained to recognize the presence of this particular scent while sitting or lying down.
After two months of training, Cliff underwent a test to see if his abilities were founded. For the test, the dog smelled 50 C. difficile-positive and 50 C. difficile-negative samples. He was able to detect all 50 positive samples, and correctly identified 47 of the 50 negative samples. This gave him a score of 100 percent sensitivity and 94 percent specificity. Sensitivity calculates the proportion of positives correctly chosen and specificity calculates the proportion of negatives correctly chosen.
Once the tests proved conclusive, the researchers took the study to the field. Cliff was taken into two hospital wards to use his sense of smell on patients. Out of 270 negative controls, he correctly identified 265 (about 98 percent). He correctly identified 25 of 30 cases (83 percent) of positive controls.
The authors noted Cliff was quick and systematic, reviewing a whole hospital ward for the presence of patients with C. difficile in less than 10 minutes.
While the study was profound, the researchers acknowledge there are some study limitations, such as the unpredictability of using an animal as a diagnostic tool and the potential for spreading infections via the dog. And still, some unanswered questions remain.
However, the team said the study does demonstrate that a detection dog can be trained to identify C. difficile with a high degree of accuracy, both in stool samples and in patients.
"This could have great potential for C. difficile infection screening in healthcare facilities and thus contribute to C. difficile infection outbreak control and prevention," the study authors conclude.