Comparison of Samples Collected by Sputum Induction and Bronchoscopy From Asthmatic and Healthy Subjects

To compare markers of inflammation in secretions obtained by sputum induction (SI), bronchial wash (50 ml instillate BW), and bronchoalveolar lavage (4 x 60 ml instillates BAL), we analyzed markers of inflammation in samples obtained by these methods in 10 healthy and 10 asthmatic subjects. Of the asthmatic subjects 8 had mild disease (FEV1, % of predicted > 75%). Within subjects from both groups, we found that sputum, compared with either BW or BAL, had higher numbers of nonsquamous cells (p = 0.0001) and higher levels of eosinophil cationic protein (ECP) (p = 0.0001), albumin (p = 0.0001), and mucin-like glycoprotein (p = 0.0001). The eosinophil percentages and the ECP levels in sputum correlated more closely with those in BW (r = 0.67, p = 0.005; r = 0.69, p = 0.0008, respectively) than in BAL (r = 0.5, p = 0.03; r = 0.37, p = 0.11). Comparing the asthmatic and healthy subgroups, we found that eosinophil percentages were higher in sputum (p = 0.0003) and BW (p = 0.006) from asthmatic subjects and that ECP levels were higher in BW (p = 0.001) and BAL (p = 0.0005) from asthmatic subjects. We conclude that analysis of induced sputum reveals information qualitatively similar to that obtained by analysis of BW and BAL and that sputum induction is not only noninvasive and easily repeated but also yields samples more concentrated and richer in airway secretions than those obtained by bronchoscopy.