In the past a persons breath would have been an important method to diagnose illnesses.
This article is at the very least interesting and I think shows great promise.
When you first hear about this study, the idea of dogs smelling cancer probably seems like the main point—and the most interesting one. But, as the story says, the goal of this study isn’t to put a German shepherd in every doctor’s office. The dogs were simply used to prove a concept: that cancer leaves some kind of distinct chemical signature on the breath. http://www.sciencenetlinks.com/sci_update.php?DocID=291
In fact, other scientists are already developing machines that can diagnose other diseases by sampling a patient’s breath: diseases like pneumonia, stomach ulcers, and even the same kinds of cancer studied here. That’s because certain diseases cause the body to produce chemicals that we normally don’t produce, or in different amounts than a healthy person would produce. Some of these chemicals find their way into the air we exhale, which means they can be smelled—if not by a human, then by an animal or a machine.
So, what’s the point of the dogs? Well, for one thing, scientists don’t yet know exactly how having cancer might change your breath, which means they don’t know what to look for. So it’s tough to build a machine—an “electronic nose”—that’s specifically tailored to look for cancer. There are electronic noses out there that just look for overall differences in odors, rather than specific chemicals, but so far, they haven’t matched the accuracy of the dogs. (One device, tested recently at the Cleveland Clinic, was 66 percent accurate in diagnosing cancer.)
Since dogs have excellent noses and are easily trained to recognize just about any odor, the dogs are like odor-detecting machines that the scientists don’t have to build. In this experiment, the researchers exposed the dogs to breath samples from known cancer patients and breath samples from healthy patients, and simply rewarded them for picking out the cancer breath. Once the dogs got the hang of it, the researchers conducted a “double-blind” trial, where the origin of the breath samples was concealed not just from the dogs, but also from the researchers themselves. With the dogs achieving up to 99 percent accuracy in the double-blind trials, the experiment shows that it should be possible to build a breath-diagnosing machine that gets it right just about every time.