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Changes in sputum eosinophils predict loss of asthma control
A Jatakanon1, S Lim, P J Barnes
1Department of Thoracic Medicine, Imperial College School of Medicine at the National Heart and Lung Institute, London, United Kingdom.
American Journal of Respiratory and Critical Care Medicine
|January 5, 2000
Summary
Reducing inhaled corticosteroid doses can trigger asthma exacerbations. Higher baseline sputum eosinophils predict these events, with increases in sputum eosinophils and exhaled nitric oxide correlating with reduced lung function.
Area of Science:
- Pulmonology and Respiratory Medicine
- Clinical Immunology
Background:
- Asthma exacerbations are often linked to increased airway inflammation.
- Noninvasive markers are needed to monitor inflammation during asthma exacerbations.
Purpose of the Study:
- To investigate noninvasive markers of airway inflammation during experimentally induced mild asthma exacerbations.
- To determine if sputum eosinophils or exhaled nitric oxide can predict loss of asthma control.
Main Methods:
- Mild asthma exacerbations were induced in 15 subjects by reducing inhaled corticosteroid dosage.
- Measurements included spirometry, methacholine airway responsiveness, sputum induction, and exhaled nitric oxide (NO).
- Subjects were monitored for 8 weeks, with exacerbations defined by peak expiratory flow, nocturnal awakenings, or beta(2)-agonist use.
Main Results:
- Seven of 15 subjects developed mild exacerbations.
- Subjects who experienced exacerbations had a significantly higher baseline sputum eosinophil count.
- Increases in sputum eosinophils and exhaled NO correlated with decreased lung function (PEF, FEV1).
Conclusions:
- Sputum eosinophil count is a potential predictor of asthma control loss.
- Monitoring sputum eosinophils and exhaled nitric oxide may aid in managing asthma exacerbations.