Asthma treatments

Editor, – Professor Seale provides an informative and helpful account of the role of anti-leukotriene drugs in asthma (Aust Prescr 1999;22:58-60), contrasting with the somewhat irrational claims of their benefits in the lay press. It raises the issue of how to assess the benefits of asthma medication. A recent study¹ advocated use of inhaled budesonide to prevent asthma relapse following discharge from the emergency department. Improved outcomes were measured by reduced relapse(defined as unscheduled visits for worsening symptoms), improved scores on an Asthma Quality of Life Questionnaire, and improved symptom scores. However there were no differences between treatment groups in measures of peak expiratory flow rates. If there is no difference in measured respiratory function, what is the significance of the other outcome measures, and what is the optimum method to assess if a patient is helped by a new intervention? If a patient says they feel better, possibly from a placebo effect of a perceived 'wonder drug', should they be continued on a new and expensive medication if there is no other measure of improvement?

Brendon Smith
Staff Specialist
Emergency Department
Sutherland Hospital
Caringbah, N.S.W.

Dr Helen Reddel, Research Scholar, Institute of Respiratory Medicine, Royal Prince Alfred Hospital and University of Sydney, comments:

Dr Smith raises an important issue about how we should assess response to asthma medications. As there is no 'gold standard' for asthma, we need to assess both subjective (symptoms, quality of life) and objective (lung function, airway responsiveness) aspects of asthma control. A marked discrepancy between the results for different outcome measures may be due to methodological problems, as seems likely in the quoted study.

The methodology for assessing relapse rate, symptoms and quality of life in this study appear to be valid, but there may be problems with the assessment of lung function. The study was designed to examine risk of asthma exacerbations, so the most appropriate lung function measure would have been peak expiratory flow performed on waking, as 'morning dipping' is associated with risk of asthma exacerbation. Lung function rises during the day even in poorly-controlled asthma, so spirometry measured at clinic visits (as in this study) would be less likely to show a difference between treatment groups. In addition, it is not clear from the paper whether lung function was measured in patients who experienced relapse and were therefore withdrawn before the 21 day assessment; if not, censoring of data from treatment 'failures' would significantly reduce the chance of observing a difference in lung function between the groups.

Dr Smith's comments about the 'placebo effect of a perceived "wonder drug"' highlight the importance of assessing the value of a new medication from a series of well-designed randomised controlled trials rather than from anecdotal reports.