Conclusions and Future Directions
Considerable variation exists in the clinical expression of asthma. As detailed in the corresponding section of this monograph, the heterogeneity of asthma is expressed clinically, by commonly observable characteristics, but these clinical phenotypes overlap and have indistinct borders. By a variety of assessment technologies and approaches (epidemiologic, physiologic, and clinical), this syndromic disease defies clear and unambiguous classification. Collectively, clinical phenotyping has not led to reliable categories of asthma that inform treatment, predict progression of lung function abnormalities, or define risk for exacerbations and death. It is for this reason that—omics approaches have been explored, and by which new stratagems for molecular phenotyping have been developed.