Dogs and humans have lived and worked together for years, earning dogs the reputation as ‘man’s best friend’, but in recent years another benefit of our four legged friends has become apparent, they could have the ability to detect certain types of diseases and cancers in humans. Organisations all over the world have realised that dogs’ sensitive noses can detect changes in odours given off by certain illnesses, and that dogs can potentially be trained to detect these conditions in humans.
Scientists believe that many diseases cause changes to occur in the body, with different organs expressing different chemical compounds. These scents are evident in breath, sweat and urine. Dogs, with their highly sensitive sense of smell, can be trained to recognise these compounds and then react to the scent of a person rather than their symptoms, making them a potentially powerful diagnostic tool.
The dogs unique ability to do this all stems from its powerful sense of smell, which is around 1000 to 100,000 times more sensitive than humans. Of course, dogs do not automatically react to the detection of these scents, a great deal of training is required to ensure that the dog acquires the correct smell and learns to react to it, but evidence has suggested that following such training dogs can be highly effective in detecting diseases in humans.
For example, recent research has shown that dogs have the ability to detect when their diabetic owners blood sugar levels are too low (hypoglycaemic), a diabetic patient can be paired up with such a dog and it can have a positive effect in helping the patient control their diabetes.
Other research has revealed that dogs can detect clostridium difficile bacteria, a bacteria that causes many hospital acquired infections.
Another area researchers are exploring is using dogs to detect cancers. Dogs are able to detect volatile organic compounds (VOCs), or odorants, that are given off in certain types of cancers. A 2011 study conducted by researchers at Medical Detection Dogs, assessed if these VOCs could be detected by specially trained dogs, in the urine of patients with bladder cancer as compared with urine samples from healthy volunteers.
The researchers found that the dogs’ specificity in detecting the cancer ranged from 56% to 92%. Dogs can also detect prostate cancer in patients’ urine, and in a small study were found to be around 97% accurate. Previous research has also found that dogs may be able to smell volatile organic compounds from a patient’s breath sample; these compounds may appear on the breath in the early stages of cancer and could be of particular interest in lung cancer detection.
Researchers in California reported that dogs can smell cancer on a human’s breath and could detect if a person had lung or breast cancer with 99% accuracy, beating the best figures from standard laboratory tests.
This doesn’t mean dogs will now be used routinely in hospital diagnostics or that you will see a Labrador sitting in your GP surgery! Our four legged friends have demonstrated to us the concept that cancer leaves some kind of distinct chemical signature that can be detected in samples from patients. Having proved the underlying principle scientists now know that if we can detect these compounds we could develop new, more accurate diagnostic tests.
As a result it has encouraged further research into developing ‘electronic nose’ sensor devices and identifying volatile chemicals that may be associated with the presence of tumours. If a device can mimic the dogs’ olfactory sense it could reduce the need for biopsies and CAT scans and detect cancer from samples of breath, blood, urine etc.
Such devices have already been devised and are currently in the testing stage, including machines that will analyse compounds in a person’s breathe. However, creating something as accurate as the dog’s nose will be quite a challenge.