Symptoms, Lung Function, and Perception of Asthma Control: An Exploration into the Heterogeneity of the Asthma Control Construct

Abstract

Background. Asthma control is still surprisingly poor, which may be related to factors causing discrepancies between objective lung function measures and subjective symptom reports or discrepancies between objective indicators of asthma control and control perception. Identifying patients prone to such discrepancies may help to understand asthma control problems. Methods. Ninety-four persons with asthma participated in this study. We used cluster analysis to identify different subgroups of asthma control, based on a measure of lung function and self-report of daytime and nighttime symptoms, activity limitations, reliever medication use, and perception of asthma control. Subsequently, we explored between-cluster differences in clinical and psychological characteristics. Results. We identified two homogeneous clusters: a cluster of persons with poorly controlled asthma and a cluster of persons with well-controlled asthma. A third cluster included persons with an intermediate level of asthma control, an absence of nighttime symptoms, and a reduced impact of asthma symptoms on daily activities despite high levels of symptoms and reliever medication use. Members of the poorly controlled asthma cluster showed higher symptom levels, more catastrophic thinking, and activity avoidance beliefs compared with members of other clusters. Conclusion. The clusters we identified crosscut current definitions of asthma severity and asthma control and indicate the importance of affective evaluation of symptoms in explaining poor asthma control.