Asthma patients were able to reduce their inhaled steroid drugs by a net 40 per cent when their dosages were tailored using a new type of breath test.
Doctors at present adjust patients' intake of drugs such as Flixotide - which prevent asthma breathlessness and wheezing - mainly based on their reports of symptoms.
But the breath-testing machine, which measures exhaled nitric oxide, has proven more effective, say Otago University researchers.
They used it in a three-year study of 94 patients, managing half with the machine and the rest conventionally.
The lead researcher, Professor Robin Taylor, said reducing inhaled steroid use by 40 per cent would save the country a lot of money on puffers.
"There was no price to pay in terms of loss of control of asthma."
The results of the study, the first to show the machine can be used to improve asthma care, are published today in a leading American journal, the New England Journal of Medicine.
One in six New Zealanders has asthma, and it is the most common cause of children's hospital admissions.
The number of sufferers is expected to rise by half in the next decade. Asthma costs the country an estimated $825 million a year in medical expenses and economic losses.
Everyone breathes out nitric oxide in low concentrations. The levels increase in people with asthma. They reduce with inhaled steroid treatment, but rise again when asthma worsens.
By measuring nitric oxide, the machine assesses inflammation in the breathing tubes of the lungs, allowing doctors to adjust the dosage of inhaled steroid.
"Our study showed that we can use nitric oxide measurements to take some of the guesswork out of deciding how much treatment to give patients with asthma," said Professor Taylor.
"In some cases, using nitric oxide results meant that the treatment dose could be reduced substantially, in some cases to almost zero. In some cases the dose has to be increased - but this was appropriate."
The machines, available since 1998, had reduced in price, now costing about US$5000 ($7059).
Professor Taylor said all public hospitals ought to have one, but only several did - including two in Auckland hospitals. A Dunedin clinic was about to become the first primary health care centre in New Zealand and Australia to have one.
A previous study by his team showed the machine was the best way to diagnose asthma.
He said that inhaled steroids were safe, but carried a degree of side-effect risk at high doses, over 1000 mcg a day of Flixotide or its equivalents.
At these doses the elderly, in particular, were at risk of thinning of the skin, bruising and eye cataracts. Getting the dosage right improved the cost/benefit ratio.
The president of Asthma New Zealand, Allen Liang, said the breath-testing method was useful but the cost of administering each test may prove prohibitive.
Dr Liang said each breath test could cost up to $80, compared to $25 for the present method of measuring patients' lung function.
"Unless there's a wider use and the price comes down in a big way, I cannot see it used widely."
Conroy Wong, who has researched the effects of inhaled steroids, believed every hospital should have the machine.
Dr Wong said research showed that people taking steroids through puffers had a very small chance of experiencing bone thinning, or osteoporosis.
The breath-test method reduced the amount of drugs taken, thus reducing the risk of bone thinning even further, he said.
"I think that, ultimately, most respiratory units should have one of those machines."
- additional reporting: Errol Kiong
The technique cuts use of inhalers by 40 per cent.
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