Correlation of induced sputum eosinophil levels with clinical parameters in mild and moderate persistent asthma in children aged 7-18 years

Background: Treatment decisions in asthma are currently based on clinical assessment and spirometry. Sputum eosinophil, being a marker of airway inflammation, can serve as a tool for assessing severity and response to treatment in asthma patients. Objectives: To measure eosinophil percentage in induced sputum in children with asthma and correlate it with clinical asthma parameters. Methods: A prospective observational study was performed at tertiary care hospital on 91 children aged 7-18 years with newly diagnosed mild or moderate persistent asthma. The induced sputum eosinophil percentage was obtained at the time of enrollment and three months after treatment with inhaled budesonide. Patients were specifically evaluated for five clinical parameters of asthma, i.e., days of acute exacerbations, use of salbutamol as rescue medication, emergency visits, nighttime cough and days of school absence. Results: Sputum eosinophil percentage was high (3.1 +/- 0.515%) at the time of enrollment which reduced significantly after three months of inhaled budesonide therapy [0.06 +/- 0.164% (p < 0.0005)]. Children with moderate persistent asthma had significantly higher values of sputum eosinophil levels than children with mild persistent asthma at the time of enrollment (3.38 +/- 0.64% vs. 2.99 +/- 0.42%, p = 0.001) but the difference was not significant after three months of inhaled steroid therapy (0.07 +/- 0.18 vs. 0.04 +/- 0.12, p = 0.5104). A significant negative correlation was found between reduction in sputum eosinophil levels and improvement in FEV1 (r = -0.400, p = 0.0001). All the clinical asthma parameters also correlated significantly with the reduction in sputum eosinophil levels after three months of inhaled steroid therapy. Conclusion: Eosinophil levels in induced sputum correlate well with clinical asthma parameters and asthma severity in children. It is a simple, noninvasive and cheap method which can be used for the monitoring of asthma in a resource-limited setting.