The sniff test has a long legacy in medicine. In ancient Greece, doctors would diagnose diseases by smelling a patient's breath. But while the human nose is strong enough to pick up on general illness, it's unlikely that it's capable of homing in on specific conditions.That's where machines can help. A recent study published by The American Chemical Society provides evidence for a disease-sniffing technology that uses sensors to identify the presence of conditions like Parkinson's, multiple sclerosis, and various types of cancer. The device works by picking up volatile organic compounds (VOCs) in the patient's breath. These VOCs arise from metabolic functions, and the researchers identified 13 that combine to give each disease its own unique "breathprint."For the study, a team of researchers led by Hossam Haick, a chemical engineer and nanotechnology professor at the Technion-Israel Institute of Technology, collected breath samples from 1,404 people. Some had no diseases, while others had one of 17, including cancers and inflammatory and neurological conditions. Subjects were asked to breathe into a chemically inert Mylar bag, and the air was transferred to tube filled with nanoparticle-packed sensors, which were tailored to detect organic compounds. After registering the various VOCs in the breath, the researchers were able to predict diseases with 87 percent accuracy. That leaves a generous margin of error, but the hit rate could be good enough to one day justify adding a breath test to your annual check-up.The idea of sniffing out disease has captivated researchers for several years, with the most promising results coming from dogs. In 2006, for instance, the California-based Pine Street Foundation trained dogs to detect breast and lung cancers by smelling breath. The dogs were 88 and 97 percent accurate, respectively.But dogs present challenges: They aren't easily transported, and training is expensive. What's more, they're typically only trained to pick up on one disease at a time, ignoring all others. A machine, on the other hand, can target multiple diseases at once—making it a more viable option as an affordable, non-invasive important first step toward detecting life-threatening ailments.