NO_x in exhaled breath condensate is related to allergic sensitization in young and middle-aged adults

Background: Asthma and allergic diseases are heterogeneous. Measurement of biomarkers in exhaled breath condensate (EBC) may help to discriminate between different phenotypes and may assist with clinical prognostication.

Objectives: We aimed to assess associations between total nitric oxide products (NO_x ) in EBC and different allergic phenotypes and lung function in young and middle-aged adults.

Methods: Cross-sectional analyses were nested within two Australian longitudinal studies, the Melbourne Atopy Cohort Study (MACS, mean age 17.8 years) and the Tasmanian Longitudinal Health Study (TAHS, mean age 49.4 years). Levels of EBC NO_x were determined by Griess-reaction fluorescent method. Associations were assessed between EBC NO_x and different allergic phenotypes, lung function and airway reactivity.

Results: Atopy, with or without asthma or rhinitis, was associated with increased EBC NO_x levels particularly in individuals with poly-aero-sensitization. These findings were generally consistent across the two age groups. In the older cohort, use of ICS in the previous 12 months masked the association between sensitization and EBC NO_x (OR = 0.64, 95% CI = 0.21-1.96, p for interaction = 0.05).

Conclusions and clinical relevance: In these population-based samples, EBC NO_x was most strongly associated with atopic sensitization, rather than either current asthma or rhinitis, possibly indicating underlying increased airway inflammation associated with atopy. Therefore, EBC NO_x could be a key predictor of atopy in both young and middle-aged adults, regardless of the presence of concomitant asthma or rhinitis.