Up to 30% of adults considered to have asthma may have been incorrectly diagnosed, the National Institute for Health and Care Excellence (NICE) has said.
NICE has issued draft guidelines on asthma diagnosis, noting that while some symptomless patients may have had asthma, others may have been incorrectly diagnosed.
The new guidelines, which are open to consultation until Wednesday 11 March 2015, recommend initially testing with a spirometer, which measures breathing speed.
NICE warned there is no "gold standard" test to diagnose asthma and most diagnoses are made after checking for signs and symptoms, rather than specific tests for asthma.
Currently about 10% of adults with asthma develop it after exposure to substances such as chemicals or dust in the workplace.
In the UK 4.1m people are receiving treatment for asthma while occupational asthma is the most common industrial lung disease in the developed world with over 400 reported causes.
The guidelines also recommend asking patients how their symptoms are affected by their work and checking patients know how to use their inhaler correctly.
Professor Mark Baker, director of clinical practice at NICE said: "Asthma is a long-term incurable condition that affects millions of people of all ages. If left untreated asthma attacks can be life threatening.
"However, with appropriate treatment and thoughtful monitoring, most people will be able to successfully control their symptoms and be spared from serious harm."
He added; "Accurate diagnosis of asthma has been a significant problem which means that people may be wrongly diagnosed or cases might be missed in others.
"Our aim with this guideline is to give clarity and set out the most clinical and cost effective ways to diagnose and monitor asthma based on the best available evidence."
