Adenosine Triphosphate Concentration of Exhaled Breath Condensate in Asthma

Background: Purinergic signaling is involved in asthma pathogenesis. Not only adenosine but also adenosine triphosphate (ATP) might play a role, but human evidence is scarce. ATP can be measured in exhaled breath condensate (EBC), a noninvasive airway sample suggested as being suitable for patient monitoring. We determined EBC ATP concentration in asthma, investigated its relation to disease parameters, and calculated airway ATP level. Methods: EBC was collected from 45 patients with persistent asthma (age 34.7 +/- 13.2 years; FEV1 87.0 +/- 15.5% predicted; mean +/- SD) and 32 healthy control subjects (age 36.9 +/- 12.6 years; FEV1 98.9 +/- 9.9% predicted). Exhaled nitric oxide concentration (FENO) and lung function were measured, and Asthma Control Test (ACT) score was obtained. EBC ATP was measured in luciferin-luciferase assay. Airway ATP concentration was calculated using dilution estimated from conductivity of vacuum-treated EBC samples. Parametric tests were applied in the analyses. ATP concentrations and nitric oxide levels were logarithmically transformed. Results: EBC ATP and calculated airway ATP concentrations were not elevated in asthma, and none of them was related to FENO or ACT score. EBC ATP concentration was influenced by airway droplet dilution (r = -0.32, P < .05), and there was a relation between calculated airway ATP level and FEV1 (r = 0.35, P < .05). Conclusions: EBC ATP concentration does not seem to be useful for asthma monitoring. The relation between EBC mediator concentration and EBC conductivity highlights the importance of further standardization of EBC methodology and the need for more studies to understand airway droplet formation. CHEST 2010; 138(3):536-542