Induced sputum: diagnostic value in interstitial lung disease.

Induced sputum by inhalation of hypertonic saline solution is a noninvasive technique used to collect cellular and soluble material from lung airways. During the past decade, this method has been widely used to assess airway inflammation in asthma and chronic obstructive pulmonary disease, since it produces reliable results and compares favorably to other invasive techniques, such as biopsy and bronchoalveolar lavage (BAL). Induced sputum has been recently used to study interstitial lung disease (ILD), more specifically pneumoconiosis, sarcoidosis, and nongranulomatous ILD. Moreover, results from induced sputum supplied information comparable to BAL findings for occupational lung disease and were able to distinguish sarcoidosis patients from healthy subjects and from patients with nongranulomatous ILD. Although induced sputum had previously provided promising results in assessing patients with ILD, its diagnostic role has not yet been well defined. Further studies of the evaluation by induced sputum of grading of severity, follow-up of disease, and effects of treatment are needed. Additionally, to date no specific studies have been undertaken to evaluate the safety and functional effects of sputum induction on patients with ILD. In conclusion, we think that induced sputum can be used as a complementary tool to BAL both in research and in clinical monitoring of patients with ILD.