Background: Assessment of exhaled breath condensate (EBC) pH is a promising method for investigating airway pathology. However, inaccurate measurement techniques may bias pH readings. In this longitudinal study, we tested whether development of bronchiolitis obliterans syndrome (BOS) in lung transplant recipients is associated with acidification of EBC.
Methods: EBC was collected in 15 patients with BOS and 16 stable BOS-free patients during routine clinical visits. From nine BOS patients, samples were collected before and after the onset of BOS, as well. Twenty healthy nontransplant subjects served as controls. EBC pH was measured by the carbon dioxide gas standardization method.
Results: EBC pH in patients with and without BOS and controls was similar (BOS group: 6.40±0.04, BOS-free group: 6.45±0.03; controls: 6.39±0.02; P>0.05). In patients who developed BOS during the follow-up, EBC pH before and after the onset of BOS was comparable (pre-BOS: 6.41±0.04 vs. post-BOS: 6.41±0.04; P>0.05). Coefficient of variation for repeated pH measurements in controls and subjects with and without BOS was 2.3%±0.3%, 2.0%±0.3%, and 1.7%±0.2%, respectively (P>0.05). Similarly, the limits of agreement for between-visit variability determined by the Bland-Altman test were comparable among the study groups.
Conclusions: These data suggest that assessment of EBC pH is of limited value for the diagnosis of BOS.