Exhaled Breath Condensates as a Source for Biomarkers for Characterization of Inflammatory Lung Diseases

Abstract

Inflammatory lung diseases such as asthma and chronic obstructive pulmonary disease are common and difficult to diagnose and characterize. This is due in large part to difficulty in obtaining samples directly from the inflamed lung. The collection of lung secretions by traditional methods including bronchoalveolar lavage and induced sputum collection are limited by their invasive nature. Exhaled breath condensate (EBC) is a simple and non-invasive technique of collecting fluid samples, which are representative of airway lining fluid. Advances in collection methods and evolving molecular techniques have led to development of more sensitive assays for existing biomarkers and identification of new biomarkers, which can be potentially useful in monitoring lung inflammation. In this review, we present the current understanding of various biomarkers including small molecules (H2O2, pH and nitric oxide related biomarkers), lipid mediators (8-isprostane, leukotrienes and prostaglandins), small proteins (cytokines and chemokines) and nucleic acids (DNA and microRNAs). We also discuss the differential profile of biomarkers in recognizing different patterns of lung inflammation. As the sensitivity of methods of EBC improves, this biofluid will play an increasing role in diagnosis and monitoring of lung diseases.