Measuring the effectiveness of asthma therapy

There is an increasing body of evidence demonstrating that the high aims stated in asthma management guidelines are not being met In order to understand how to optimise asthma treatment, the effectiveness of therapy must be assessed, addressing the issues of appropriate: 1) outcome measures, 2) study design for comparison of different therapeutic approaches, 3) duration for assessment of outcomes, and 4) presentation of outcome information. The different impact on outcome measures seen with asthma therapy, and the different focus of patients and healthcare professionals, implies that more than one measure is required to assess asthma control. Appropriate outcome measures include symptoms, impact of symptoms on patient lifestyle, use of rescue medication and exacerbations (assessed by use of oral steroids, emergency consultations and hospital attendance). A number of attempts have been made to integrate different outcome measures, although currently there is little agreement on the approach to take, making comparisons between trials problematic. Although randomised clinical trials may be the gold standard for efficacy studies, they do not represent real life and so provide limited information on effectiveness. A nonhierarchical approach to appraisal of evidence, in which different study designs are seen as complementary since they fulfil different needs, may be appropriate. Studies need to be of sufficient duration for long-term assessment and data should be presented such as to allow assessment of the likelihood of treatment success.