title: Asthma entities.
abstract: Asthma is a syndrome characterized by variable airflow limitation, airway hyperresponsiveness and airway inflammation. Considering asthma in aggregate, it is clear that a number of distinct mechanisms underlie the development of this disorder. In some patients, the mechanistic distinctions can be clearly drawn, and important therapeutic insights can be gained. In other patients, several mechanisms may coexist, or it may be impossible to separate them with current methods and technology. To distinguish subsets of asthma is more than an academic exercise. For both clinicians and asthma researchers, it is valuable to distinguish asthma subtypes as clearly as possible. Clinicians strive to prescribe the most effective, most safe, and most cost effective therapy possible, and understanding asthma subsets and their underlying mechanistic differences can substantively facilitate achieving that objective. Asthma research is often limited by significant, and sometimes dramatic intersubject variability. It is likely that at least some of that variability may arise from the (unrecognized) mechanistic heterogeneity of asthma. Better definition and selection of more homogeneous subsets of asthma may then lead to greater statistical power, and more definitive conclusions from asthma investigations.
authors.affiliation: Asthma Program, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, USA.
authors.forename: W J
authors.initials: WJ
authors.lastname: Calhoun