Thousands of people are being treated for asthma when another condition may be the cause of their illness, according to new research.
The study is being discussed at the annual scientific meeting in Auckland of the Thoracic Society of Australia and New Zealand.
Asthma is the leading respiratory disease diagnosed in New Zealand, Australia, Canada and the United States.
Three of the world's leading asthma researchers, Professor Robin Taylor (Otago University), Professor Peter Gibson (John Hunter Hospital, Newcastle, NSW) and Professor Ian Pavord (Leicester University, England), have studied and validated several new tests that allow a more accurate assessment of the patient.
The tests can tell the clinician whether they are under-treating or over-treating the patient or whether in fact the diagnosis of asthma is accurate or not.
Damage to the small breathing tubes during childhood or adolescence when they are more vulnerable may lead to symptoms which may mimic asthma.
Making an accurate diagnosis is essential to good management and may save the country millions of dollars in medication costs.
The new tests, which are available only in a few New Zealand hospitals running clinical trials, suggest that a significant proportion of people being treated for asthma because of a chronic cough, wheeze or chest tightness may have other inflammatory conditions that respond better to other medications.
Doctors are not suggesting people throw away their inhalers but are saying that a few specific tests such as expired nitric oxide measurement, sputum analysis and CT scans could differentiate between asthma and damaged airways.
If the disease is not asthma, patients will respond more readily to different medication regimens and enjoy a better quality of life.
"The challenge for the Thoracic Society will be to evaluate ways of transferring the results of [laboratory] tests ... into the clinical workplace," said Auckland branch president Dr Jeff Garrett.
"The results of the studies being conducted in our leading hospitals ... will hopefully give us more direction."
* About 1 in 6 New Zealanders have asthma - about 656,000 people.
* Asthma medications account for between $60 million and $80 million of the pharmaceuticals budget.