Differences in exhaled breath condensate pH measurements between samples obtained with two commercial devices

Background: The objective of this study was to determine differences in EBC pH between samples obtained by RTube and EcoScreen, and to identify the effect of storage at -80 degrees C on the pH values. Methods: Twenty-three nonsmoking subjects with asthma or allergic rhinitis or without respiratory disease performed two sequential exhaled, breath condensate (EBC) collections, using the RTube collection system and the EcoScreen condenser. EBC pH was measured immediately after collection and after storage at -80 degrees C for 8 weeks, without deaeration and repeated following deaeration with Argon. Results: In EBC samples without deaeration, the EcoScreen pH values were significantly higher than the RTube pH values (mean difference, 0.32; 95% CI, 0.21-0.44, P < 0.0001). In deaerated EBC samples, the EcoScreen pH values were also significantly higher than the RTube pH values (mean difference, 0. 12; 95% CI, 0.01-0.25, P = 0.04). For both EBC collection systems, storage for 8 weeks had a significant influence on pH of nondeaerated samples. Conclusions: The present study demonstrates that EBC pH value is dependent on the collection device used and that the storage for 8 weeks had a significant influence on the pH of samples analyzed without deaeration. (c) 2007 Elsevier Ltd. All rights reserved.