Induced sputum in patients with interstitial lung disease: a non-invasive surrogate for certain parameters in...

Induced sputum is a useful non-invasive method for the assessment of airway and parenchymal lung diseases. This study aimed to compare induced sputum and bronchoalveolar lavage fluid (BALF) cellular composition and T-lymphocyte subpopulations in patients with interstitial lung disease. We evaluated 33 patients: 15 with sarcoidosis, 11 with hypersensitivity pneumonitis, and 7 with idiopathic pulmonary fibrosis. The percentage of macrophages was significantly lower in induced sputum than in BALF in sarcoidosis (P=0.005), and the percentage of neutrophils was higher in induced sputum than in BALF in sarcoidosis (P=0.001) and hypersensitivity pneumonitis (P=0.006). A significant correlation was found between the BALF and induced sputum CD4+, CD8+ subsets and the CD4+/CD8+ ratio in both the whole patient group (r(s)=0.80, r(s)=0.88, r(s)=0.88, P<0.001, respectively) and in the 3 subgroups. A strong correlation of the T-lymphocyte subsets in induced sputum and BALF in patients with interstitial lung disease shows that induced sputum may be a non-invasive surrogate for certain parameters in BALF in these patients.