Sensitive Noses in the Hospital
(June 30th, 2015) Detecting dangerous infections and even cancer in its early stages is important but not easy. Luckily, clinical science can increasingly rely on man’s best friends, dogs.
When Hotsche Luik and Michel Grobbe, both dog trainers, came to the University of Wageningen to talk about the amazing ability of dogs to sniff cancer, I was impressed, to say the least. But how do they do it?
First of all, Michel Grobbe mentioned that the sniffing capabilities and efficacy of dogs is 100 times better than ours. Dogs possess approximately 1,300 olfactory receptor genes, 3 times more than humans. It’s also well known that they can be trained to recognise and memorise odour signatures of explosives or drugs, for instance. It’s less well known that dogs are also able to help diagnose diseases.
During their presentation Michel Grobbe and Hotsche Luik (sharing the stage with Hotsche’s dog, Cliff) showed that the 5-year old Beagle is able to clearly identify a patient infected with the dangerous hospital pathogen Clostridium difficile. It is important that the dog is friendly and kind, the dog trainers explained. When Cliff smells an infection he will not approach the patient but sit in front his bed.
Hotsche Luik trained Cliff for only 2 months to recognise the specific odour of the toxigenic C. difficile strain on culture plates. All sorts of materials like wooden sticks, plastic vials or fabrics were marked with the bacterial strain’s odour and used as training material. In the end Cliff successfully learned to differentiate the scent of the bacterial strain in a wide range of settings, including stool samples and infected patients. And Cliff’s sensitivity and specificity are stunning. The team who worked with him at a Dutch Hospital said he recognised infections in stool samples, with 100% accuracy and in patients in 25 of 30 cases.
But dogs are capable of so much more, even detecting cancer. This has been suspected since 1989 when a dog owner, alarmed by his dog’s unusual attention towards one of his moles, sought medical advice and was diagnosed with a malignant melanoma.
Nowadays, dogs can reliably detect prostate cancer, too. A recent publication by an Italian research group suggests that given appropriate training dogs can exceed standard blood tests for prostate cancer in terms of both, sensitivity and specificity.
What dogs smell are so-called “volatile organic compounds” (VOCs) released by the prostate cancer cells. These are excreted in the urine and are pattern-specific. At the Italian hospital the two German Shepherds, Zoe and Liu, easily identified prostate cancer in urine samples with a sensitivity of 98-100 % and a specificity higher than 97%.
The detection rates clearly exceeded the existing standard blood test for prostate cancer in which prostate specific antigen (PSA) is measured in blood samples. The dogs’ superior cancer detection ability comes in very handy as the regular PSA test faces growing criticism due to its low specificity which is especially concerning for the early detection of prostate cancer. Good to know that training of the two dogs took only 5 months. It was, however, a full time job for a team of 4 people: a chief medical veterinary surgeon, a trainer and 2 assistants.
Some questions remain about the practicality and consistency of the dog method in clinical practice, but there is reason for being optimistic. Michel Grobbe pointed out that the potential predictive value of this procedure can only be achieved by building up a good infrastructure with screening centres, common training academies, and good collaboration of participating laboratories.