Clinical application of exhaled breath condensate analysis in asthma: Prediction of FEV₁ improvement by steroid therapy

Background: Exhaled breath condensate (EBC) measurements have recently been reported to be useful for the detection of inflammatory molecules in the airways. However, the clinical relevance of EBC analysis in asthma therapy has not been determined yet. Objectives: To investigate whether EBC analysis has any potential for predicting the steroid response in asthmatics. Methods: Eighteen steroid-naive asthmatics were enrolled. EBC collection, spirometry and a methacholine challenge test were performed before and 12 weeks after inhaled steroid therapy. Exhaled IL-4, IL-17, RANTES, macrophage inflammatory protein (MIP)-1α, MIP-1β, IL-8, IFN-γ-inducible protein (IP)-10, TNF-α and TGF-β were simultaneously analyzed by a protein array, and the relationship between baseline molecule expression and steroid-mediated changes in forced expiratory volume in 1 s (FEV₁) and airway responsiveness was investigated. Results: Steroid therapy improved FEV ₁ values and the methacholine threshold. Among the molecules examined, increased IL-4 and RANTES levels as well as decreased IP-10 levels at baseline were significantly correlated with an improvement in FEV₁. By contrast, molecule levels were not related to changes in the responsiveness to methacholine. In addition, changes in FEV₁ values were significantly associated with reductions in IL-4 and RANTES levels. Conclusions: EBC measurements of IL-4, RANTES and IP-10 might be useful for predicting the steroid-mediated FEV₁ improvement in asthma.