Comparison of induced sputum and bronchoalveolar lavage in lung transplant recipients

Chronic lung rejection is characterized by obliterative bronchiolitis (OB) diagnosed based on spirometric criteria reflecting an already advanced process. Biologic markers such as bronchoalveolar lavage (BAL) neutrophilia or increased levels of chemokines (interleukin-8, RANTES [regulated on activation: normal T cell expressed and secreted]) have been proposed as early diagnosis tools. However, BAL is too invasive to be used as a routine strategy. Induced sputum (IS), however, is a non-invasive method of recovering bronchial cells.

The aim of this study was to compare BAL and IS differential cellular counts as well as IL-8 and RANTES levels between patients with bronchiolitis obliterans syndrome (BOS), recipients with good outcome and well-preserved lung function (non-BOS) and non-transplanted controls. We compared 34 BAL and IS findings obtained consecutively from 34 lung transplant recipients (LTRs), including 22 non-BOS and 12 BOS patients.

IS results were compared with 19 samples from non-transplanted controls. IS was well tolerated. There was no correlation between BAL and sputum cell populations. BAL neutrophils and IL-8 levels were increased in BOS, and these parameters were positively correlated. Moreover, BAL neutrophils and IL-8 levels were both negatively correlated with respiratory function. Sputum evaluation allows discrimination of BOS from non-BOS by the presence of higher neutrophil and eosinophil counts. Moreover, IS neutrophils and eosinophils were both correlated with lung function parameters. In contrast to BAL, IL-8 level in sputum was not a useful predictive marker of BOS development. IS RANTES levels were higher in BOS than in healthy recipients and correlated significantly with IS eosinophils.

IS and BAL provide different but complementary data. In this study, IS appeared to be a useful, non-invasive tool for LTR monitoring. Furthermore, IS provides new insights into BOS pathogenesis, especially with regard to implication of eosinophils and its chemokine, RANTES, at the bronchial level.