Article Text

Outcome measures in asthma
  1. M THOMAS
  1. The Surgery, Minchinhampton
  2. Stroud, Gloucs GL6 9JF, UK
  3. drmthomas{at}oakridge.sol.co.uk
    1. N C BARNES
    1. Department of Respiratory Medicine
    2. The London Chest Hospital
    3. London E2 9JX, UK

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      As Neil Barnes points out in his review of outcome measures in asthma,1 the selection of appropriate outcomes plays a key role in shaping clinical and research agendas. He relates widely used outcome measures to the aims of management as stated in current asthma guidelines, particularly in terms of parameters of long term asthma control such as prevention of symptoms, minimal requirement for reliever medication, normalisation of lung function, and prevention of exacerbations. These parameters correspond to the aims of asthma management in the BTS2 and the GINA guidelines.3 The importance of looking at a number of different outcomes and of recognising the different time scales over which these outcomes need to be measured is now widely recognised in the evaluation of medical interventions in asthma.

      It could be argued, however, that even the wide range of parameters considered in the review fails to capture all the aims of asthma management, and particularly may miss those outcomes determined by the patients themselves. It is becoming increasingly clear that patients and their doctors do not always share the same perceptions of what is important in asthma management and what constitutes a successful outcome of asthma care. The AIR study4 shows that patients are particularly concerned with functional outcomes—what matters most to them is what they can and can't do because of their asthma, and how their asthma prevents them from doing the things they want to do. Although there is obviously an overlap with other outcome measures such as symptoms, patients frequently modify their lifestyle to prevent symptoms occurring, so asthma may disproportionately impair their quality of life even in the absence of reported symptoms.

      Functional and patient determined outcomes are given surprisingly little attention in the stated aims of current guidelines. They are barely touched on in the aims statement of the BTS guidelines (“. . . minimisation of absence from school and work”) and skirted over in the 1999 GINA guidelines (“. . . have productive, physically active lives”). The 1993 GINA guidelines aims statement covers the area more fully, with the aim to have “no limitation on activities, including exercise”. Quality of life and health status tools, which are increasingly used as outcome measures in asthma clinical trials, are perhaps beginning to move us in the direction of patient centred outcomes. The Juniper AQLQ questionnaire5 in particular does include patient determined functional outcomes as part of the assessment of health status.

      In daily clinical practice we aim to elucidate and address our patients' goals and aspirations, and they form a major part of our clinical decision making process. Perhaps the time has come for us to develop and validate tools to capture these important outcomes in clinical trials of asthma interventions. The outcome measures outlined in the review all reflect different and complementary aspects of overall asthma management, but they are generally physician centred. There is also a need to capture data on patient centred and functional outcomes. This is particularly true of the pragmatic real world studies that are needed to clarify the position and merits of the increasingly wide array of therapeutic options open to us in the everyday management of asthma.

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      author's reply I would like to thank Dr Thomas for his interest in my article. He is critical that patient centred outcomes were not included in my discussions. Patient centred outcomes have been increasingly discussed, but a number of questions need to be answered before these are accepted. Just because health care practitioners and patients are using different words or terminology does not mean they are not interested in the same objective. A patient's desire to be able to play sport and a practitioner's aim to prevent exercise induced asthma are just different ways of articulating the same goal. Furthermore, patients may have an incomplete understanding of their disease and the consequences of different forms of management. A patient may consider that an important outcome to them is to be able to stop all their inhalers and to smoke 20 cigarettes per day without getting wheezy, but I doubt that Dr Thomas would think that either of these were reasonable outcome measures to look at in a clinical trial. The physician must not only listen to patients' concerns, but must also educate them as to the short and long term consequences of particular behavioural and treatment patterns. Unless care is taken, uncritical acceptance of patient centred outcomes may have negative as well as positive features. Furthermore, it needs to be established in well controlled clinical trials that adding patient centred outcomes makes a fundamental difference to clinical trial outcome. My paper was also about the interrelationship between different outcome measures. It is difficult to make comparisons when measures cannot be repeated frequently, and at present most research using quality of life questionnaires just administers these at the beginning and end of a trial, so comparisons with lung function, symptoms, and β2 agonist use which can be measured frequently and changes in quality of life are difficult.

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