Eosinophil Count and Eosinophil Cationic Protein Concentration of Induced Sputum in the Diagnosis and Assessment of Airway Inflammation in Bronchial Asthma

Abstract

Measurement of eosinophil percentages and ECP concentration in induced sputum may be useful in the diagnosis and assessment of the variability of airway inflammation in bronchial asthma (BA). To evaluate the usefulness of sputum eosinophil counts and ECP concentrations in the diagnosis of BA, we measured these parameters in 68 patients with respiratory complaints. In addition, we followed-up 14 BA patients with variable airflow limitation for 45.4 +/- 10.4 days. The BA group (n = 41) showed a higher percentage of sputum eosinophilia (24.5 +/- 7.6 vs. 2.2 +/- 2.9%, p < 0.001) and a higher level of sputum ECP (198.2 vs. 90.6 micrograms/L, p < 0.05) than those in the nonasthmatic group (NBA, n = 27). The sensitivity and specificity of sputum eosinophilia (> or = 5%) for the diagnosis of BA were 85.4% and 92.6%, respectively, which were better than the sensitivity (68.3%) and specificity (55.5%) of the increased level of sputum ECP (> or = 100 micrograms/L). Patients with moderate-to-severe persistent BA had a higher percentage of sputum eosinophil (n = 23, 34.6 +/- 10.6%) than those of mild persistent BA (n = 18, 10.7 +/- 5.2%, p < 0.01), but we could not find significant difference in ECP levels between mild persistent and moderate-to-severe persistent asthma. The percentages of sputum eosinophilia showed a moderate correlation with ECP (r = 0.4358, p < 0.01) and with the peak expiratory flow rate (PFR, r = -0.4746, p < 0.01) but sputum ECP did not correlate with PFR. In 14 BA patients who were followed, there was a relationship between changes of PFR and the percentage of sputum eosinophil (r = -0.7238, p < 0.01), but the change of PFR did not correlate with the change of sputum ECP levels. These results suggest that the sputum eosinophil count and sputum ECP level could be helpful in the diagnosis of BA, but that sputum ECP is not satisfactory for the assessment of variability of airway eosinophilic inflammation during the initial anti-inflammatory management of BA.

Effect of pranlukast on bronchial inflammation in patients with asthma

“…reported that bronchial eosinophil recruitment and activation may occur even in mild to moderate stable asthma and that bronchial epithelium damage and airway responsiveness may be partially associated with the eosinophilic inflammatory reaction [8]. There is also much evidence that bronchial asthma is characterized by chronic recruitment of eosinophils to the airways, and eosinophils play an important role in bronchial epithelial damage in asthma by releasing cationic proteins [9–11]. Allergen exposure in atopic asthmatic patients is associated with recruitment and activation of eosinophils in the airways.…”

“…Eosinophils release toxic products, including the eosinophil cationic protein (ECP), which damage bronchial structures, and increase bronchial hyperresponsiveness once they are activated [12]. Serum ECP is thought to be a useful marker of eosinophilic inflammation in bronchial asthma [9–11,13].…”

House dust mite-specific IgE antibodies in induced sputum are associated with sputum eosinophilia in mite-sensitive asthmatics

“…The validity of the cut-off value of sputum eosinophil count (Ն5%) used in this study also has been verified by another group using 41 asthmatic patients and 27 nonasthmatic subjects. 12 We conclude that allergen-specific IgE antibodies in induced sputum from atopic asthmatics are associated with sputum eosinophilia. This result suggests that IgE-dependent mechanisms are involved in eosinophilic inflammation of the airway in atopic asthmatics.…”

“…We chose this cutoff value on the basis of our previous study 11 and the validation of sensitivity and specificity by another group. 12 …”

Serum B12 Tryptase Level as a Marker of Allergic Airway Inflammation in Asthma

“…However, a marker of airway inflammation does not necessarily correlate with asthma severity. For example, recent studies have shown that there is no correlation between sputum eosinophilia, a hallmark of airway inflammation in asthma, and asthma severity (10), and between sputum ECP levels and pulmonary function (11). We speculate that factors other than airway inflammation, such as airway remodeling, might also contribute to asthma symptoms and airflow limitation.…”