To the Editors:

Exhaled breath condensate (EBC) analysis is a simple and truly non-intrusive approach to acquire information on understanding airway inflammation and other diseases of the respiratory system, such as tumourigenesis 13. There are several striking advantages to utilising breath testing for screening purposes: 1) it does not influence airway function or cause inflammation 4; 2) it can be performed repeatedly within short intervals 5; 3) it is not significantly affected by age, sex or disease status 5; and 4) it can be considered as a lung-specific analytic approach. Cancer cells have distinct properties from normal cells in that they may synthesise new proteins or change the protein expression levels during tumourigenesis 6. A lot of soluble components of the lung exist in the epithelial lining fluid of alveoli 7; therefore, the secreted new synthetic proteins can be digested into peptides under enzymatic processes. Subsequently, the small peptides have the possibility of adding to exhaled breath like other EBC compounds. The exploration of endogenous peptides, created by enzymatic cleavage of proteins in particular cellular environments, can result in relevant biomarker candidates 8, 9. However, trace amounts of materials in EBC make detection a challenging task. This study was designed to determine the peptidome of EBC and to search for potential biomarkers for lung cancer diagnosis.

The study protocol was approved by the Institutional Review Board of the Kaohsiung Medical University Hospital (Kaohsiung, Taiwan). Patients with histological evidence of primary lung cancer who were admitted to the Division of Pulmonary and Critical Care Medicine (Dept of Internal Medicine, Kaohsiung Medical University Hospital), between January 2008 and August 2008 were enrolled in the study. We enrolled patients with squamous cell carcinoma, adenocarcinoma, small cell carcinoma, pneumonia and chronic obstructive pulmonary disease …

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