GC-MS vs. Dog

This weekend I’ve bathed my two dogs, Nika who is a Siberian husky and Cara who is a labrador. For some reason they are still moulting in July!

Looking at Cara’s comical face, ball and drool hanging from her mouth, it is easy to forget that dogs are incredible animals that are helping humans in many different ways.

They guard us, herd our livestock, guide the blind, listen for the deaf and help disabled people with household duties. They are truly remarkable animals. Because their sense of smell so much more superior than that of our own they work in our airports to prevent drug smuggling and protect our armed forces from land mines. The British army currently has about 400 sniffer dogs trained to find explosives and weapons. The dog’s nose is so sensitive it can detect components below 500ppt (part per trillion) levels. When Cara smells the curry that is cooking in my kitchen she can distinguish individual ingredients in the complex mixture, she can smell every herb and every spice.

Anyone who has a dog will tell you that they know when you are ill. Nika knows when I am ill or feeling under the weather. She lies beside me and looks after me. But I’ve read stories which go further than this, stories where a pet dog has obsessed over their owner’s mole until they got it checked out by a doctor…and it turned out to be a malignant melanoma. At first it is easy to pass it off as the rambling misconceptions of neurotic pet owners, but actually there is truth to these stories.

It is well-known that cancer cells release volatile organic compounds. This is because the cell’s metabolic functions are not normal and as a result their products are different to that of normal cells. Cancer cells release chemicals such as methanol, acetone, ketones and aldehydes, as well as some hydrocarbons. Scientists have cultured cancer cells in a sealed container and collected the gases given off. These gases have then been analysed using gas chromatography mass spectrometry (GC-MS).

Shimadzu GC-MS

Results have shown that many different volatile gases are given off by diseased cells which are not given off by normal cells. These gases are then exhaled in our breath.

So if dogs can detect the individual ingredients of a curry, can they detect the individual components of our breath such as the chemicals given out from disease? The answer is yes. Dogs have been used to detect breast and lung cancer in patients by smelling their breath with outstanding results.

This amazing diagnostic ability of the dog has been known since 1989 when Williams et al published “Sniffer Dogs in the Melanoma Clinic” in the Lancet. Since then there has been many tests and trials and results have shown that dogs can be trained in three weeks to become medical detection dogs.

And it’s not just cancer that dogs can sniff out they can also detect low blood sugar level for diabetes patient, alerting them to take medication. Even our unsophisticated human noses can detect “sweet breath” as a sign that someone has diabetes. It’s caused by the breakdown of fats and proteins for cellular energy, the breakdown causes acid compounds called ketones to form in the blood. This is known as ketoacidosis and as a result the patient breath smells of the ketone, acetone. We can smell it because the levels are high enough, but imagine if our sense of smell was more sensitive like that of the dogs. What other chemicals could we detect which would indicate disease?

This amazing canine ability is now being used by research facilities, NHS trusts and universities. A charity has been set up in Milton Keynes which trains specialist dogs to detect the odour of human disease. This charity is called Medical Detection Dogs and trains dogs to assist individuals manage complex medical conditions on a day-to-day basis. The dogs are separated into two sections cancer & bio-detection and medical alert dogs. Dogs are taught to identify the odour changes associated with certain medical events. For example if a patient has diabetes, a Hypo Alert Dog recognises when blood sugar levels are outside the normal range and warns their owners or gets help, before the symptoms are felt. They even bring their owner any necessary medical supplies such as glucose and blood testing kits and can be trained to push alarm buttons.

Medical alert dogs may soon be as common as guide dogs and could dramatically improve quality of life for many people. In addition bio-detection dogs may prove to be an non-invasive way of detecting many diseases such as cancer at an earlier stage.

So from a scientists point a view, can the dog’s nose really rival a GC-MS? We know that a dog’s nose has good sensitivity and can detect down to parts per trillion levels and like chromatography, it can separate out components of very complex mixtures. But a GC-MS will not bring you any medical supplies or raise the alarm. Looking at Cara now, drool still hanging for her chops, I see that she is much more than a companion, her nose is actually a very advanced piece of analytical instrumentation.