The American Thoracic Society and the European Respiratory Society have released official standards for clinical trials and practice with respect to the assessment of asthma. The statement appears in the July 1 issue of the American Journal of Respiratory and Critical Care Medicine.
“In the past, there has been no standard way of assessing asthma. This has led to a lot of confusion for doctors who are managing asthma, and in research, it was difficult to compare the results of different studies,” said Helen Reddel, M.D., Ph.D., from the Woolcock Institute of Medical Research in Sydney, Australia, and co-chair of the international task force with D. Robin Taylor, M.D., Ph.D., from the University of Otago in Dunedin, New Zealand.
The American Thoracic Society and European Respiratory Society set up the task force of 24 asthma experts from North America, Europe, South Africa, Australia and New Zealand, to provide standardized definitions and measurement recommendations for three main areas: asthma control, asthma severity and asthma exacerbations.
Asthma control was defined as the extent to which the features of asthma have been reduced or removed by treatment, with respect to both current clinical control and future risk. The explicit inclusion of future risk is a change from the previous approach that had mainly focused on current clinical control.
“The addition of future risk is important for three reasons: first, because some medications can improve symptoms while not treating the underlying disease; second, because some patients are at increased risk of asthma attacks despite having few symptoms; and third, because medication side-effects should be taken into account when deciding a patient’s need for treatment,” said Dr. Reddel.
To assess future risk, the report found that the most robust predictors were frequency of asthma exacerbations, repeated measures of lung function, and treatment side-effects. However, Dr. Reddel noted, “if a study is not long enough to measure these directly, the task force provided recommendations about surrogate markers such as sputum analysis or bronchial challenges which can predict the risk of these outcomes.”
The task force found that no single measure of asthma control could be recommended at present for use in clinical trials, but developed a short list of standardized endpoints, which were divided up into essential, desirable and optional. They recommended symptom-free days, reliever use, lung function, quality of life and a validated composite score as robust measurements for current clinical control. Other measurements which may be considered include a daily diary (preferably electronic) and a record of visits to doctors and the emergency room.
Asthma severity was defined as the intensity of treatment required to achieve good asthma control. “In the past, asthma severity was usually defined before a patient started asthma treatment, using measures which were almost identical to those used to assess asthma control. This was very confusing, and it meant that asthma severity could not be re-assessed once treatment had started,” explained Dr. Reddel.
Asthma exacerbations were defined as events where symptoms worsen enough to require a change in treatment. For clinical trials, the task force standardized the definition of severe asthma exacerbations (also called severe attacks) as events that require urgent treatment such as corticosteroid tablets over three or more days in order to prevent serious consequences.
The task force made the clinical recommendation that doctors routinely ask every asthma patient a few simple questions about their asthma symptoms and management both in the short- and long-term: for the past one to four weeks, how many days a week they have had symptoms, how much quick-relief medication have they used, and whether they have woken at night from asthma; and for the past year, how many times they have had severe attacks, since this can identify patients who are at risk of severe attacks in the future.
“In clinical practice, it is particularly important to measure lung function for the diagnosis of asthma, and also for assessment of patients whose asthma is troublesome either because they have a lot of symptoms despite treatment, or because they have few symptoms but a lot of severe attacks,” said Dr. Reddel. For both research trials and clinical practice, the task force report provided detailed information about how each endpoint should be measured, the range of normal values and how the measurement should be interpreted.
The statement further stressed the need for more research, which will make the assessment of asthma control simpler in the future.
“More research is needed to understand more clearly how asthma control — and risks for asthma exacerbations – can be best assessed for the different types (i.e., phenotypes) of asthma, which have different responses to therapy,” John Heffner, M.D., past president of the ATS confirmed. “The task force identified that studies will need to characterize the clinical features of study patients during enrolment to ‘type’ their asthma and then note patterns of treatment responses for each type. With enough information, accurate type-specific measures to assess asthma control will emerge that will guide physicians in adjusting therapy for each phenotype.”
Future directions of research were suggested at the end of each section, and the statement concludes with an eye toward the possibility of identifying and determining appropriate biomarkers and for some groups of patients relying on those, rather than symptoms, to determine the appropriate medical treatment.