Every human has a "breathprint" – what does yours say about you?

The chemical signature in your breath is unique to you, and may even be as distinctive as your fingerprint. In fact, researchers think your "breathprint" could soon be used to determine your true identity, or diagnose you with an illness.

For years, medicine has relied on blood, urine, and tissue samples to monitor wellness and disease. These biological samples contain metabolites – leftovers from the biochemical processes that keep a body running – that can convey important information about a person's health. A given metabolite profile depends on a variety of factors: diet, infection, circadian rhythms, the microorganisms living in your gut. They all affect the type and quantity of chemicals present in your body's various organs and biofluids – including, it turns out, your breath.

When you exhale, you expel more than nitrogen, oxygen, argon and CO2. There are also metabolites. But here's the question: do the metabolite concentrations in expired air vary enough from person to person (and are they consistent enough within a single individual) to be diagnostically useful?

Recent findings suggest they do. In 2011, researchers proved that dogs can be trained to reliably detect lung cancer on the breath of hospital patients. Earlier this month, scientists demonstrated that a breath test could be used to diagnose stomach cancers with 90% accuracy. Now, research presented in the latest issue of the open access journal PLOS suggests that each and every one of us has a unique breathprint, providing some of the most compelling evidence to date that a person's breath can serve as a valuable (and minimally invasive) diagnostic tool.

The study, led by analytical chemist Renato Zenobi, examined the metabolite profiles in breath exhaled by eleven participants. The researchers collected samples four times a day for a total of nine days, and used a technique known as mass spectrometry to identify and quantify the biomolecules present in each sample.

Write the researchers:

Consistent with previous metabolomic studies based on urine, we conclude that individual signatures of breath composition exist. The confirmation of the existence of stable and specific breathprints may contribute to strengthen the inclusion of breath as a biofluid of choice in metabolomic studies. In addition, the fact that the method is rapid and totally non-invasive, yet individualized profiles can be tracked, makes it an appealing approach.

The researchers observed significant, identifiable differences in the chemicals on each participant's breath. As hypothesized, they also identified variation between samples taken from the same person at different times of day, but these variations were still well within each person's very distinct "core" breathprint. In other words: a person's breathprint may change from day-to-day, or even hour-to-hour, but it is still highly specific. It is still very much theirs.

And as the researchers point out, breathprinting is minimally invasive. Unlike a blood test, there's no need for needles or fingerpricks; and unlike a urine sample, there's no need to drop your pants. And the results from the mass spectroscopy are given almost instantly.

Further study is obviously necessary. A longer-term study, involving more participants, would be useful in tracking if and how breathprints change over time in response to sickness, health, or changes in diet. Do breathprints vary within and between populations? Could they serve any forensic purpose? Which biomolecules correspond to which diseases? How much forewarning can they offer us? These are questions worth investigating. For now, however, this study provides an important proof of concept: your breathprint says a lot about you, specifically. What might yours say about you?

The researchers' findings are presented, free of charge, in the lates issue of PLOS.

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