Cluster analysis and clinical asthma phenotypes.

Rationale: Heterogeneity in asthma expression is multidimensional, including variability in clinical, physiologic, and pathologic parameters. Classification requires consideration of these disparate domains in a unified model.

Objectives: To explore the application of a multivariate mathematical technique, k-means cluster analysis, for identifying distinct phenotypic groups.

Association between neutrophilic airway inflammation and airflow limitation in adults with asthma.

Background: There is debate about the mechanisms of persistent airflow limitation in patients with asthma. Chronic inflammation is assumed to be important, although there is limited and contradictory information about the relationship between airway inflammation and postbronchodilator FEV1.

Methods: We have assessed the cross-sectional relationship between prebronchodilator and postbronchodilator FEV1 and measures of airway inflammation after allowing for the effects of potential confounding factors.