Exhaled breath condensate nitrite/nitrate and pH in relation to pediatric asthma control and exhaled nitric oxide.

BACKGROUND: Combining exhaled breath condensate (EBC) and exhaled nitric oxide (eNO) may be a useful, non-invasive method to assess airway inflammation in pediatric asthma. This cross-sectional study evaluated the relationship of both EBC nitrite/nitrate (NOx) and EBC pH with asthma control and eNO in asthmatic, normal, and atopic children.

METHODS: A total of 92 children were recruited, comprising 62 with asthma, 14 with atopy only, and 16 who were normal and non-atopic. All completed a questionnaire for asthma symptoms and control. Variables measured were spirometry, EBC NOx, pH, and eNO.

RESULTS: EBC NOx in those with asthma (mean 8.4 microM, CI 7.5-9.4) was significantly elevated when compared with normal (4.8 microM, CI 3.4-6.2, P = 0.0007) and atopic children (6.5 microM, CI 4.0-9.1, P = 0.02). The mean level of eNO was significantly higher in those with asthma (43.7 ppb, CI 34.7-51.1, P < 0.001) and atopy (24 ppb, CI 16.7-31.2, P < 0.05) when compared with normal children (11.5 ppb, CI 6.7-16.2). There was a significantly lower pH in those with asthma and a FEV(1) < 80% predicted (P = 0.03), but no significant overall differences in EBC pH between the three groups of children. There was a significant correlation between eNO and EBC NOx in the group as a whole, but not between eNO and EBC pH.

CONCLUSIONS: Mean EBC NOx levels differ between children with asthma, atopy, and those who are normal, but it is not interchangeable with eNO. EBC pH may be an additional marker of asthma control.