A saliva test for asthma developed by British scientists could provide a simple and more effective way to identify and monitor the condition.
The lung function tests currently used can be inaccurate and other procedures involving blood or urine samples may be distressing for children.
Testing saliva for signature "biomarkers" - chemicals linked to asthma - could be carried out easily without upsetting even the very youngest patients.
Lead scientist Professor Colin Creaser, from Loughborough University, said: "Unlike other sampling methods, such as expired breath analysis, saliva can be collected by passive drool from the very young to the very old without causing distress."
Before the test can be rolled out for general use it will have to be validated by further studies.
As well as helping to spot early signs of asthma, the test could be used to track the severity and progression of the disease, said the researchers.
The findings are published in the journal Analytical Methods.
To develop the test, the Loughborough team, working with colleagues from Nottingham City Hospital, collected saliva from both asthma patients and healthy individuals.
They then used a technique called liquid chromatography mass spectrometry to analyse the chemical make-up of the samples. Metabolic biomarkers were identified that provided an asthma molecular "fingerprint".
Around 5.4 million people are currently being treated for asthma in the UK, including 1.1 million children.
Dr Samantha Walker, director of research and policy at the charity Asthma UK, said: "There is no single, simple test to diagnose asthma because it is such a complex condition with many different causes which we are yet to fully understand. This research suggests a saliva test could potentially be a simple way to diagnose asthma in the future.
"However, this research into saliva tests was carried out with a relatively small group of only 30 people, and it will need testing in much larger numbers before we have a good picture of how effective it could really be in diagnosing asthma.
"It is critical we see greater investment into research like this that will help us to diagnose asthma more accurately, along with research to better understand and treat it as we work towards a cure."
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