ABSTRACT
I. Epidemiology Exacerbations of asthma still remain a relatively common cause of unscheduled medical care. Defining the exact incidence of exacerbations of asthma is difficult as there is no universally accepted definition of an asthma exacerbation. However, if an operational definition of requirement for emergency treatment is used then questionnaire surveys performed in many different countries show a rate of asthma exacerbations varying between 7% and over 40% (1)
There is no universally accepted definition of an asthma exacerbation. Patients almost never use the term asthma exacerbations; they talk about an asthma attack, which for some individuals would mean some wheeze that causes them to take a bronchodilator and for others would mean a severe attack that might lead to attendance at an accident and emergency department or a hospital admission. In clinical trials there has been equally confusing use of the terms asthma attack and asthma exacerbation. In some trials, the term asthma exacerbation has been used to describe an increase in symptoms, up to 20% decrease in peak expiratory flow (PEF), and an increase in rescue b2-agonist use with the term asthma attack being reserved for requirement for treatment with oral steroids or a larger 30% or more decrease in PEF (2). The FACET study was one of the first trials that had prevention of exacerbations as one of its main outcome measures (3). There were two definitions of exacerbation: severe exacerbation was requirement for a course of oral corticosteroids or a 30% fall in PEF from baseline and a mild exacerbation was an increase in bronchodilator use or an increase in symptoms on two consecutive days. There were about 20 times the number of mild exacerbations compared with severe exacerbations and it is now considered this definition of mild exacerbation is really just an increase in symptoms. Each patient’s experience of an asthma exacerbation is different. An individual with well-controlled asthma and good lung function may seek advice and emergency treatment more readily than an individual who has generally poorly controlled asthma, which is used to dealing with a worsening of their asthma without recourse to medical care.
