Abstract
Introduction: Longitudinal trials have suggested that asthma control may be influenced by fluctuations in eosinophilic inflammation. This association has however never been confirmed in daily practice.
Aims: To investigate the relationship between asthma control, sputum eosinophils and maintenance asthma treatments in daily practice.
Methods: A retrospective longitudinal study was conducted in 187 asthmatics who underwent at least 2 successful sputum inductions at the University Asthma Clinic of Liege. Linear mixed models were performed to assess the relationship between asthma control and individual changes in sputum eosinophils, and between the sputum eosinophil count and individual variations in asthma treatments. ROC curves were constructed to define cut-off variations in sputum eosinophils associated with a change of at least 0.5 in Asthma Control Questionnaire (ACQ).
Results: In intermittent/persistently eosinophilic asthmatics, a multivariate analysis showed that asthma control was associated with individual fluctuations of sputum eosinophil, but not neutrophil, count (p<0.01). We calculated a minimal important decrease in the percentage of sputum eosinophils of 4.3% (AUC:0.691, p=0.0001) or 3.4 folds (AUC:0.648, p=0.003) for a significant improvement in asthma control and a minimal important increase of 3.5% (AUC:0.675, p=0.004) or 1.9 folds (AUC:0.634, p=0.02) for a significant worsening in asthma control. Among asthma treatments, only the changes in inhaled corticosteroid (ICS) dose influenced the sputum eosinophil count.
Conclusions: At the individual level, asthma control was associated with fluctuations in sputum eosinophil count over time and the latter was influenced by changes in ICS dose.
- Copyright ©ERS 2015
