Breath test: grid search for diseases

Dr. Andrea Bannert has been with since 2013. The doctor of biology and medicine editor initially carried out research in microbiology and is the team's expert on the tiny things: bacteria, viruses, molecules and genes.She also works as a freelancer for Bayerischer Rundfunk and various science magazines and writes fantasy novels and children's stories.

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Your breath is a mirror of your health: Thousands of markers tell you what you have eaten, whether you have smoked or which diseases lie dormant in you. Optical noses could help to identify threatening diseases very early in the future. Even cancer.

The human lung is a huge organ - its total surface area: 100 square meters. This enables a lively exchange between breathing air and blood. In the lungs, it is not just the blood that is oxygenated. In the alveoli, the air is also loaded with all sorts of substances from the blood. The exhaled air thus becomes a characteristic fingerprint of the human metabolism. Over 3000 different molecules are buzzing around in it.

Optical snoopers

Hippocrates used his nose for diagnostic purposes 2500 years ago: the smell of ammonia was a sign of liver or kidney failure and anyone who smelled of fresh bread from their mouth may have had typhoid. Today optical sniffing noses take over. They can provide initial indications of diseases such as asthma, diabetes, liver and kidney problems, various infectious diseases or cancers such as lung or breast cancer. And earlier than previous methods - and much more pleasant for the patient. Because all he has to do is blow into a tube. Like the alcohol test on the street.

Why does it work? For some diseases there is a specific marker in the exhaled air: a lot of nitric oxide reveals asthma, for example, in breast cancer patients the breath is enriched with pentane, in lung cancer patients with acetaldehyde. "Often, however, it is combinations of several molecules that are characteristic of a certain disease," explains Prof. Boris Mizaikoff from the Institute of Analytical and Bioanalytical Chemistry at the University of Ulm in an interview with Such marker combinations exist for many more diseases than previously known. However, they would first have to be deciphered piece by piece.

Breathing gas fingerprint

Mizaikoff and his team are currently working on a measurement method for breathing air that is particularly sensitive and can be packaged small. "Such a measuring device that could be used in a doctor's office would then be the size of the palm of your hand." Previous devices are too bulky and too expensive - so they are not suitable for routine use.

With Mizaikoff's measuring system, the breathing air is irradiated with infrared light. This causes the molecules in the breathing gas to vibrate. And every molecule vibrates differently - depending on how it is structured. “This is called the molecule's characteristic infrared fingerprint,” says Mizaikoff. With the method, several trace gases can be measured with high detection sensitivity within a few minutes.

As sensitive as mammography

The Ulm researchers want to test their measurement methodology for breast cancer patients in the long term. The biggest advantage: Breathing gas analysis saves women the radiation exposure of a mammography. In addition, the breast does not have to be pressed flat between the X-ray plates, which can be very uncomfortable for the patient. And: The days of waiting for the result would also be a thing of the past with the infrared sniffing test.

In a first test, the analysis correctly diagnosed 70-80 percent of women using volatile, small molecules, but still using laboratory measurement methods. An earlier study by American scientists achieved a similarly good result with a different measuring system: 48 out of 51 patients were correctly identified. This means that the breath test can easily keep up with the mammography screening in terms of informative value.

Nevertheless, Mizaikoff and his colleagues want to improve their method even further - by combining it with other measurement methods, such as fluorescence measurement. The researchers hope to be able to turn the sensitivity screw again vigorously. "If at some point you can measure very small differences, you could not only prove the disease yourself, but also check the success of the treatment with this gentle examination," hopes Mizaikoff.

Disruptive factor nutrition

However, there is still one problem: The breathing gas is not only influenced by illnesses. Many other factors also play a role: for example, what you ate, whether you smoke or not, what ambient air you breathed or whether your circulation has changed.

“The system has to learn to differentiate such causes from the information relevant to the disease,” says Mizaikoff. In the next step, the researchers want to feed the measuring system with the data from a large number of test subjects. "For our clinical studies we not only need sick and non-sick people, but also as many different lifestyles as possible in both groups in terms of diet, smoking and other factors."

Blow once, please

It will take a few more years before the doctor's puff test becomes a routine examination. "For changes that are easier to measure, it could be in a year or two," says Mizaikoff. One example is the liver function test that the researchers have already successfully tested on mice: The animals were fed glucose with marked carbon atoms in their food. If the glucose is metabolized, the infrared measuring device recognizes the mark in the breath. And provides a direct measure of how well the liver is working.

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