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Compounds in an exhaled breath are found to be useful to medical diagnosis.

Metabolites found in your breath represent the waste products of your body's chemistry, acting as an individual "fingerprint," according to scientists.

A breath test can provide instant results, unlike blood or urine tests which have to be sent to a lab for testing and can be just as useful in medical diagnosis, according to a Plos One study.

"I don't understand why breath hasn't been a widely used [means of] medical science diagnosis," said the study's lead author Renato Zenobi of the Swiss Federal Institute of Technology in Zurich.

The researcher compares this technique to traditional Chinese medicine, where doctors "feel your pulse, look at your tongue and smell your breath." Zenobi even mentions trained dogs ability to "sniff cancer with a fairly good hit-rate," in an article in BBC News.

Previous research has shown that particular bacteria responsible for lung infections and even stomach cancer can be distinguished in a breath. However, scientists still questioned whether the breath's metabolic contents varied enough between people, yet remained stable enough in an individual in order to provide a diagnostic analysis.

Researchers took breath samples from 11 volunteers across four time slots for nine working days. The samples were run through a mass spectrometer, which effectively measures all masses of the chemical compounds in the breath, according to BBC News.

"You need to show there is a core individual signal that is stable over time," Zenobi said. "If it changes a lot during the course of the day or after you've had a coffee or smoked a cigarette, you can just forget about it."

Research showed that some compounds, such as water vapour and carbon dioxide, were the same in all participants, but other compounds which differed proved to be unique to individuals. These compounds remained stable through the course of the experiments.

The immediate and non-invasive nature of the breath test makes it promising because it could help determine an appropriate dosage in anesthesia, which is dependent on a patient's tolerance and metabolic rate.

Further verification of an individual's unique "breathprint" could lead to "personalized medicine" which would be tailored specifically to an individual's body chemistry.  

While the current testing equipment is a large, laboratory based system, the equipment is likely to be miniaturized similar to a modern breathalyzer.

The researchers are currently working with pulmonologists to detect signs of lung diseases such as asthma, sarcoidosis and cancer in an effort to eventually reach medical diagnosis from a patient's "breathprint."

"We're at the onset of learning about what the compounds are. Just a small fraction of the peaks that we see are identified at this point, so there's a lot of footwork to be done."