Imagine a world where the only medical diagnostic test needed was a small box with flashing lights, like the tricorder used in the TV series Star Trek. You would just wave it in the air near the patient and instantly find out what was wrong with them. This is science fiction, but perhaps we may be getting one small step towards that.
We all produce chemicals as by-products of our bodies’ metabolic processes and many of these can exist as a vapour. This vapour can have a smell - body odour and bad breath are examples of that. But sometimes these vapours can hint at something more sinister, like the presence of disease. This fact has been known for millennia and there is documentary evidence that physicians in ancient Greece used odour in diagnosing disease. The smell of rotten apples on breath indicated diabetes, and sputum which produced a particularly foul odour after being thrown in the fire was evidence of tuberculosis.
Not much was done with this information until the 1970s when researchers, including the double Nobel Prize winner Linus Pauling, started to investigate the composition of breath using sophisticated scientific instruments of the day. Technical difficulties remained for many years but these approaches have now been re-vitalised with the discovery that animals can detect various diseases. You probably already know that police sniffer dogs can detect drugs and explosives. Well one pet dog kept licking his owner’s mole and seemed fascinated with it. When the owner went to see the doctor, the mole was found to be cancerous, so the dog’s exquisitely sensitive nose turned out to be a rapid cancer detector!
Dogs are now being used more widely in detecting cancer, but dogs are not the only animals used in detecting disease. Bees and African giant pouched rats have been trained to sniff out disease too – primarily tuberculosis, ideal for use in a developing country where complicated laboratory tests are difficult.
Animals are not ideal in a clinical setting (who wants to have to breathe on a rat?), but what they do tell us is that there is an odour associated with a disease. My research aims to use sophisticated equipment, such as a mass spectrometer, to try and find out what it is that the animals are actually smelling.
So, what do we actually sniff? Well, initially breath seemed like the best idea because people are happy to give breath samples; after all, we all do it quite happily in public all the time. But sometimes breath is difficult, for instance when the sample needs to be stored. So over the years, we have in fact sniffed breath, blood, serum, urine, poo, sputum and skin. And there’s no need to stop there, in fact any bit of a person can be sniffed depending upon the illness.
The diseases or conditions we have applied this approach to include certain cancers, diabetes, tuberculosis and gastro-intestinal related diseases. Many other people have extended this to look at a range of other cancers and infectious and metabolic diseases.
So who knows, one day it may just be a quick sniff of your body with a small box of tricks and the Star Trek tricorder may look a bit dated!