WHEEZING IS BELIEVABLE!

There is often justifiable suspicion about what an asthmatic says; ‘reporting to please the doctor’, or to avoid reproach, is very well proven in studies of compliance with asthma medication and peak flow readings, using electronic monitors. And anyway, medical science is rarely happy without objective evidence, like FEV1 or bronchial hyper-reactivity (BHR), before reaching valid conclusions. This began to change with the international (ISAAC) study, originating in New Zealand, which provided descriptions of asthma which were accepted world-wide for comparing asthma prevalence rates amongst children, and the trend continues.

An Australian study finds that when the patient says “I experienced wheezing during the past 12 months”, without any objective measurement, this is a more reliable indicator of 'Quality of Life', than is a measurement of BHR combined with a report of wheezing (ref 1). This is in opposition to the recent adoption of the two findings together which had been adopted as a useful definition of 'current asthma' for epidemiological studies. The point is made that for the asthmatic, symptoms restricting lifestyle are what matters. The subjects were 426 adults 26–50 years old.

A study in Finland also concluded, in respect of 218 children 7–12 years old, that BHR should not be required for defining asthma in epidemiological studies(ref 2). 'Clinical asthma' was confirmed by a pediatric allergist with a combination of symptoms with at least one objective clinical, lung function or challenge test. But the authors found that a final diagnosis of asthma was only marginally increased by including an objective test.

A UK study agrees: “It is concluded that retrospective recall of wheeze at age 8–13 years is a valid proxy measure for the lifetime prevalence of wheeze” (ref.3). A cohort of over 1,000 was surveyed for the third time at ages 8–13 using questionnaires from the ISAAC Study. The question at the third survey was “Has your child ever had wheezing or whistling in the chest at any time past?” There was good correlation with responses to the earlier surveys.

EXERCISE-INDUCED ASTHMA

In the Finnish study mentioned above (ref.2), only 35% of the asthmatic children had a positive 8-minute 'free-running test' (a consequential 10% or greater reduction in airflow being sometimes used as an alternative to methacholine inhalation for defining BHR.)

Most of them did indeed have a greater airflow reduction than most non-asthmatic children; but then 2.9% of these 'normal' children also reached the 10% reduction to be classed as positive, to be described as having exercise-induced broncho-constriction without asthma, like some long-distance runners in the Finnish winter. Both groups would do well with a pre-exercise reliever inhalation.

Night cough. Another interesting finding from the Finnish study was that 8% of children whose only complaint was dry cough at night, had a positive free-running test. Does this mean they did have asthma? It becomes easy to see why experts cannot agree on an absolute definition of asthma!

References:
1) Thorax 2002;57:165-67
2) Ibid 120-26;
3) Eur Resp J 2000;16:80-85