Blog by Gabi Newton, postgraduate student in the School of Medical Sciences.

Researchers at The University of Manchester are investigating whether the air we breathe out could provide clues to help diagnose asthma – potentially offering doctors a new, non-invasive way to understand what is happening in the lungs.

For many people, getting an asthma diagnosis isn’t straightforward. Symptoms such as coughing, wheezing, chest tightness and breathlessness can be caused by several conditions. Asthma can also change over time, meaning symptoms and test results may vary.

Research suggests around 30% of asthma cases may be misdiagnosed, potentially leading to inappropriate treatment or delays in receiving the right care.

So, could our breath provide another clue?

What’s in our breath?

Every time we breathe out, we release hundreds of chemicals known as volatile organic compounds (VOCs). These may provide clues about processes taking place inside our lungs.

Researchers are investigating whether people with asthma have patterns of these chemicals – like a chemical “fingerprint”.

Dr Waqar Ahmed, a Research Fellow and the University of Manchester, works in a team of scientists, clinicians and statisticians led by Professor Stephen Fowler. Together, they are exploring how chemicals in exhaled breath could improve our understanding and diagnosis of respiratory conditions.

What have the researchers found?

A recent University of Manchester study involved people referred by their GP with suspected asthma, who were assessed by respiratory specialists at Wythenshawe Hospital. Everyone had breathing problems that could have been asthma, but after specialist assessment, some were diagnosed with asthma and others were not.

This is important because previous breath research has often compared people with established asthma with healthy volunteers, rather than people experiencing similar symptoms. Participants provided breath samples for VOC analysis, which were used for research and not to make their diagnosis.

Researchers also sampled the surrounding air, as environmental chemicals can influence what is detected in our breath. Three VOCs – ethyl butanoate, 2-methylfuran and 3-methylpentane – showed the most consistent differences between those with and without asthma. Whilst they could not diagnose asthma alone, they provided useful information when combined with existing clinical tests.

As Dr Ahmed explains:

“We’ve moved on from asking ‘can we find a disease biomarker?’ to ‘what detailed information can breath profiles tell us about biological processes and environmental exposures?’”

This could help researchers understand not only disease, but what is happening in the body and what people are exposed to.

Could breath tell us more about asthma?

Another study by the same group explored whether breath could identify different types of airway inflammation.

Researchers analysed 74 people with asthma or chronic obstructive pulmonary disease (COPD). Statistical analysis distinguished the groups with 93.2% accuracy and identified breath patterns associated with different types of inflammation.

This could eventually help doctors understand a person’s condition more precisely and choose treatments better suited to them. Breath analysis could also offer a more patient-friendly alternative to sputum analysis, which can be uncomfortable and difficult to perform.

What’s next?

Blood and urine tests often have clear instructions for collecting samples, such as fasting before a blood test or providing the first urine of the day. VOC breath analysis does not yet have the same level of standardisation.

Time may be particularly important. Our bodies follow a natural 24-hour cycle called the circadian rhythm, and Manchester research has shown that levels of some VOCs change depending on the time of day. The timing of inhaled corticosteroid medication can also affect these patterns which is particularly important for asthma diagnosis.

Researchers therefore need to consider factors including sample timing, medication and environmental exposure to produce reliable results and move VOC analysis towards clinical use.

What could this mean for people with asthma?

VOC breath analysis isn’t currently used as a routine asthma test. More research and standardisation are needed before it could be introduced into everyday healthcare.

Rather than replacing existing tests, VOC analysis could provide doctors with another piece of the diagnostic puzzle – potentially helping identify asthma and different types of airway inflammation.

For people struggling to get a clear diagnosis, this could ultimately mean receiving the right treatment sooner.

In the future, the chemical fingerprint in our breath could tell doctors much more about what is happening inside our lungs.

Additional information

This is the first in a new series of research articles. Would you mind taking a few minutes to complete some feedback? Thank you.

Asthma research article – Fill in form

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