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The concept that treatment with inhaled corticosteroids (ICS) may improve long term lung function by reversing or minimising the effects of airway remodelling remains an attractive one but, until now, unproven. It is therefore with much interest that we read the publications of two observational studies by Lange et al1 and by Dijkstra et al.2 Both groups of authors hypothesised that asthmatic individuals continuously treated with ICS would have a less pronounced decline in forced expiratory volume in 1 second (FEV1) than those not treated with ICS, and their studies indeed suggest that long term treatment with ICS in asthmatic adults is associated with a more favourable decline in FEV1 with age compared with the natural course of the disease.
Obviously, the most interesting next question is to what extent further improvement in FEV1 is possible. Unfortunately neither study addressed the issue of possible additional anti-inflammatory treatment. The assessment of FEV1 after maximal bronchodilation and a course of systemic corticosteroids in these groups of patients would have been most interesting because it might show the maximal attainable functional outcome in adults who have had asthma for many years.
Similarly, one could study growth of lung function in childhood and adolescence to assess whether this is affected by asthma and can be reversed by anti-inflammatory treatment. Lange et al,1 Dijkstra et al,2 and the accompanying editorial by Ernst3 refer to the CAMP study4 as one which showed that ICS treatment may not even improve FEV1 in children with mild asthma compared with placebo. The CAMP study did indeed assess lung growth from postbronchodilator FEV1 as the primary outcome variable, but it lacked the proper design to address this issue fully because bronchodilation was not maximal and ICS treatment was started in a daily dose of 400 μg and tapered off or stopped based on symptoms. Because treatment based on symptoms does not take into account of—and is likely to underestimate—the degree of inflammation,5 such a study design is probably biased towards underestimation of the maximal attainable level of function.
In our own study we observed that FEV1 after maximal bronchodilation was normalised in children with moderately severe asthma who continued to inhale 600 μg budesonide daily, and also when they had become completely asymptomatic.6 This suggests that ICS treatment can completely normalise FEV1. Whether similar favourable effects of ICS on postbronchodilator FEV1 can also be demonstrated in adult patients with long term asthma is unknown.
We therefore think that future long term outcome studies in adults with asthma should try to estimate the maximal attainable lung function.
Review history and Supplementary material
Competing interests: none declared.
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