For years, humans’ best friends have helped provide unconditional comfort and support for those coping with medical challenges. Dogs have made an enormous impact in the world of therapeutic patient care, offering their dedicated services to people with physical and emotional issues. Now, canines are poised to offer an extraordinary level of assistance in yet another crucial way—detecting potentially life-threatening diseases.
The path to this intriguing new frontier was paved by Eastern medicine. Traditional modalities have leveraged smell for thousands of years, helping to detect and diagnose a range of ailments. The first published report of scent-identified human disease is thought to have appeared in a Chinese medical text from the 3rd Century B.C. Ancient papers on the subject include commentary from the Greek physician Hippocrates, mentioning the overall scent change of feverish patients.
For dogs, the world is defined by scent. Their noses may be cold, wet, and cute, but they’re also astonishing anatomical structures, capable of detecting scents on the order of parts per trillion. Neuropsychological researcher and renowned author Stanley Coren notes that—depending upon breed— canines can have as many as 300 million nose-based scent receptors. Compare that to the olfactory ability of human beings, who have about five million.
The noses of both species are comprised of scroll- shaped plates called turbinates, which contain scent-detecting cells. The area housing our own human odor-analyzers measures approximately one square inch, about the size of a postage stamp. In our loyal hounds, however, the total surface area is estimated to be as large as 60 square inches, closer in size to a standard sheet of copy paper.
The part of a canine’s brain dedicated to processing aroma is roughly 40 times more powerful than our own, says Coren. That makes a dog’s sense of smell approximately 100,000 times sharper than a human’s. To put this in perspective, we bipeds can detect a teaspoon of honey in our tea. Our dogs can detect a teaspoon of honey in a million gallons of water.
The typical canine snout also has the ability to discern specific, individual components. Think about the welcoming aroma of baking bread. We humans take in a single cohesive scent: bread. But our dogs can distinguish the flour, eggs, butter, milk, salt, and yeast.
For all of these reasons, doctors and researchers have started to consider the complex challenges of disease detection from the perspective of a pup’s powerful proboscis. The goal is to put these cold, wet canine noses to work identifying illnesses and saving human lives. So far, global studies seem to confirm rather impressive levels of accuracy.
Currently, researchers and trainers are examining this premise for a growing range of ailments. When it comes to cancer in particular, modern science recognizes that tumors exude minuscule amounts of alkane and benzene derivatives referred to as volatile organic compounds (VOCs)—elements not found in healthy tissues. These metabolic waste products are often excreted during the earliest stages of disease onset. And if they’re there, it’s reasonable to wonder if a dog’s highly sensitive nose could pick up their scent.
The Pine Street Foundation is a small, California-based non-profit on the cutting edge of bio-detection research with canines. Michael McCulloch, PhD, the foundation’s research director, is closely involved with many of these studies. He acknowledges that results to date have been astonishing, highlighting the need for further chemical analyses of the key components actually being detected.
In a study done by McCulloch and researchers in California, Utah, and Poland and published in the medical journal Integrative Cancer Therapies, dogs were trained to detect lung malignancies in the breath of cancer patients. The canines performed this task with up to 99 percent accuracy. The bio-detection dogs were also correct roughly 88 percent of the time for breast cancer identification, with virtually no false positives. This level of precision compares favorably to mammogram statistics, where the potential for false-positives tends to increase with the number of mammograms a woman undergoes.
Many bio-detection research canines have been temporarily borrowed from either private caregivers or foundations like Guide Dogs for the Blind. But with research continuing to gain momentum, dedicated teams of dogs are now being trained to sniff preserved, physician-collected bio-samples such as breath, perspiration, urine, blood, and saliva. Organizations like North Carolina-based Blue Ridge Medical Detection Dogs, California- based In Situ Foundation, and Medical Detection Dogs UK are on the forefront of using positive reinforcement methods to coach these canines in scent detection of medical ailments.
While a range of breeds can be used, Medical Detection Dogs UK notes that working breeds with a “high hunt drive” tend to demonstrate the most consistent task dedication. In Situ frequently uses shelter and rescue dogs, and is one of the first organizations of its kind to participate in collaborative, published research studies with leading institutions such as Duke University and UC Davis. According to the organization’s web site, it takes more than 300 sample specimens— and anywhere between 6-8 months—to effectively train and certify a bio-detection dog.
Despite a growing range of promising data, many experts agree that the challenge remains one of pure volume. Evolving screening methods, such as bio-detection by canines, need to offer a reliable degree of accuracy, affordability, and consistency across a tremendous number of samples. Len Lichtenfield, MD, Deputy Chief Medical Officer for the American Cancer Society, acknowledges that canine accuracy to date has been “fascinating and absolutely noteworthy, with a surprisingly high degree of specificity.” He notes that modern technology is still striving to replicate exactly what these dogs are doing. “One would hope that we could eventually develop a chemical signature that reflects what these canines are actually detecting through scent,” explains Lichtenfeld. “That would help us translate this process into a useful, highly accurate screening tool with very widespread application.”
McCulloch points to a number of electronic nose or “chemo-receptor” studies already well underway. “The next plateau is being pursued pretty ambitiously by both universities and private companies,” he observes, adding that “over a dozen groups worldwide are working toward this level of mechanization.”
Certainly, it’s improbable that bio-detection dogs may altogether replace traditional medical testing and diagnostic equipment. Yet it’s promising to think that specialized canine scenting capabilities could help change the game in a meaningful way. Modern medicine is headed toward an unprecedented paradigm shift, one based upon the uncanny olfactory ability of dogs to “sniff out” health issues in their earliest stages. Perhaps it’s just one more reason to classify canines as our best friends.
To date, several favorable studies suggest that bio-detection dogs hold particular promise for the identification of lung, breast, colorectal, bowel, and urological cancers, as well as certain dangerous infections. Dogs have been trained to identify E.coli, facilitating more accurate diagnoses of UTI infections in disabled patients, and researchers in the Netherlands taught a Beagle to sniff out the highly contagious intestinal bacteria Clostridium difficile (or C. diff) in hospitals. If this approach can be generalized to a larger number of real- world settings, it can help contain the spread of life-threatening infections.
Promise also lies in the continued emergence of medical alert dogs trained to assist people with challenging health conditions. For example, dogs have shown an ability to detect subtle, systemic scent shifts related to a disorder called Postural Tachycardia Syndrome (PoTS). This syndrome involves an abnormal response of the autonomic nervous system which can lead to abrupt heart rate fluctuations, pronounced dizziness, even sudden fainting when the human body assumes an upright position. Soon, specialized canines could help alert patients to an impending blackout.
Diabetes is another key example. Studies suggest that a canine’s sense of smell can detect even minor changes in blood sugar levels, not to mention certain other endocrine-related hormones. Dogs are therefore being trained to assist patients with Type 1 diabetes and Addison’s Disease. When certain levels fluctuate outside of a designated range, scent-sensitive canines are able to warn patients, track down human help, or fetch life-saving medical supplies.
Detection dogs are even being trained to assist individuals who struggle with food allergies. For some patients, merely inhaling an aroma like peanut butter can trigger life-threatening anaphylaxis episodes. Medical Detection Dogs UK is currently training canines to identify airborne allergens simply by sniffing the air. An alert dog who detects problematic aromas can then warn individuals against entering a potentially dangerous area.
Work in this area continues to show increasing breadth and promise. Again and again, our dogs prove that they are uniquely equipped, willing, and able to help save—and safeguard—human lives.