Asthma is one of the most prevalent chronic diseases in children and adults. Despite effective drugs and evidence based guidelines, most people with asthma have suboptimal control, even in countries with free access to medical care and drugs. Several reasons may be at play.

To control asthma, a sequence of events must be successfully accomplished by patients and doctors, including patient awareness that symptoms are bad enough to seek medical care; adequate diagnosis and recognition of poor control by the doctor; accurate identification of the source of poor control (environmental triggers, adherence, inhalation technique, comorbidity, suboptimal treatment, or combinations thereof); appropriate adjustment of treatment if indicated; and sufficient patient adherence to both drug based and non-drug based recommendations. Any break in the sequence can lead to poor control.

Consequently, to assess the benefit of a drug, efficacy trials call for objective confirmation of the diagnosis, careful patient selection with regard to control and comorbidities, rigorous drug prescribing, and close monitoring of subjects, all of which result in higher drug use than typically seen in clinical practice.

Meta-analyses of efficacy trials have clearly confirmed the superiority of low dose inhaled corticosteroids over leukotriene receptor antagonists (LTRAs) given as monotherapy and of long acting β2 agonists over LTRAs as adjuncts to inhaled corticosteroids.