Induced Sputum versus Bronchoalveolar Lavage Fluid in the Evaluation of Patients with Idiopathic Pulmonary Fibrosis

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Abstract
Induced sputum (IS) has been proposed as a useful noninvasive method for the assessment of airway diseases. Bronchoalveolar lavage fluid (BALF), an important tool for evaluating interstitial lung diseases, has limited utility due to its invasiveness and the difficulties of performing it in severely ill patients, while it is impractical for follow-up evaluation. The aim of this study was to investigate the differences and the possible correlation of cell differential and lymphocyte subpopulations between BALF and IS samples in patients with idiopathic pulmonary fibrosis (IPF). We studied prospectively 20 patients (18 male, 2 female) of median age 67 years (range 40-75) with IPF and 10 normal subjects (5 female, 5 male) of median age 59 years (range 36-70). IS was performed with hypertonic saline solution using an ultrasonic nebulizer (Ultraneb 2000). BALF was performed by a conventional procedure using fiberoptic bronchoscopy within 3 days from IS. May-Grunewald-Giemsa-stained preps were differentially counted and T-lymphocyte subsets were analyzed by a flow-activated cell sorter. The percentage of macrophages was significantly lower in IS than in BALF (p < 0.0001), while the neutrophils were lower in BALF (p < 0.0001). A significant correlation was found between BALF and IS eosinophil counts (r = 0.54, p = 0.01) and CD4+/CD8+ ratio (r = 0.74, p < 0.0001). Our data suggest that different information is obtained by IS and BALF and thus, the two methods are complementary in IPF.