The Usefulness of Induced Sputum Examination in the Diagnostic Evaluation of Selected Chronic Inflammatory Diseases of the Respiratory Tract

Introduction: Based on the normal values for inflammatory cell counts in induced sputum produced by healthy individuals living in the region of Silesia, Poland, we assessed the usefulness of cytological examination of induced sputum in the diagnostic evaluation of asthma, chronic obstructive pulmonary disease (COPD) and chronic bronchitis. Material and methods: We analyzed the results of examinations performed in 96 healthy individuals (controls), 42 patients with asthma, 49 with COPD and 30 with chronic bronchitis. We performed spirometry with salbutamol reversibility testing and examination of induced sputum in all the subjects. Those without contraindications underwent methacholine challenge testing. Results: We found a significantly elevated percentage of eosinophils in all the patient groups compared to the controls (p < 0.00001). Median values were 10.3% for asthma, 1.5% for COPD, 1.6% for chronic bronchitis and 0.3% for the controls. We found statistically significant differences in the mean neutrophil percentages in induced sputum between healthy individuals and asthma patients, COPD patients and chronic bronchitis patients (p < 0.05). The median values were 45.75%, 38.1%, 77.5% and 58.1%, respectively. The percentage of subjects with positive eosinophil counts (>2.8%) in the sputum of patients with asthma, COPD, chronic bronchitis and in the controls was 85%, 38%, 20% and 6%, respectively. Conclusions: 1. Cytological examination of induced sputum is a good test supporting the diagnostic evaluation of chronic inflammatory diseases of the respiratory tract. 2. The percentage of eosinophils in induced sputum exceeding 2.8% is a very good indicator of asthma.