Rationale: Exhaled breath condensate (EBC) is increasingly studied as a noninvasive research method of sampling the lungs, measuring several biomarkers. The exact site of origin of substances measured in EBC is unknown, as is the clinical applicability of the technique. Special techniques might be needed to measure EBC biomarkers. Objectives: To assess biomarker concentrations in clinical disease and investigate the site of origin of EBC, we compared EBC and bronchoalveolar lavage (BAL) biomarkers in 49 patientsundergoing bronchoscopy for clinical indications. Measurements: We measured exhaled nitric oxide, 8-isoprostane, hydrogen peroxide, total nitrogen oxides, pH, total protein, and phospholipid (n 33) and keratin (n 15) to assess alveolar and mucinous compartments, respectively. EBC was collected over 10 min using a refrigerated condenser according to European Respira- tory Society/American Thoracic Society recommendations, and BAL performed immediately thereafter. Results: 8-Isoprostane, nitrogen oxides, and pH were significantly higher in EBC than in BAL (3.845 vs. 0.027 ng/ml, 28.4 vs. 3.8 M, and 7.35 vs. 6.4, respectively; p 0.001). Hydrogen peroxide showed no difference between EBC and BAL (17.5 vs. 20.6 M, p not significant), whereas protein was significantly higher in BAL (33.8 vs. 183.2 g/ml, p 0.001). Total phospholipid was also higher in EBC, but keratin showed no difference. No significant correlation was found between EBC and BAL for any of the biomark- ers evaluated either before or after correction for dilution. Conclusions: In clinical disease, markers of inflammation and oxida- tive stress are easily measurable in EBC using standard laboratory techniques and EBC is readily obtained. However, EBC and BAL markers do not correlate.
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