Evaluation of exhaled nitric oxide and nitric oxide metabolites in exhaled breath condensate during asthma

Abstract

Rationale The collection of exhaled breath condensate (EBC) represents a potentially important non-invasive diagnostic tool to sample non-volatile substances from the lower airways. The purpose of the present study was to evaluate whether there exists a relationship between exhaled nitric oxide (ENO) and NO metabolites in EBC in asthmatic patients. Methods We measured ENO (off-line and on-line) as well as nitrite (NO 2 −) and nitrate (NO 3 −) concentrations in exhaled breath condensates (EBC) from 10 normal individuals, 11 steroid-naïve, and 8 steroid-treated asthmatic patients. In all subjects, EBC was collected during tidal breathing using the Jaeger Ecoscreen system and nitrite/nitrate concentrations in EBC were measured using a chemiluminescence detector. Results ENO was elevated in steroid naïve asthmatic patients compared to healthy individuals (32 ± 23 vs 10 ± 6 ppb) and it was statistically significantly reduced in steroid treated individuals (11 ± 5 ppb, p<0.05). Nitrate but not nitrite concentrations showed an increase in steroid naïve and a reversal in steroid treated patients. Consistent with these findings, there was a positive linear correlation between ENO and nitrate but not nitrite. Conclusions Our results suggest that determination of nitrate but not nitrite might represent a relevant marker in asthma. In addition, there was a trend in increased interleukin-8 and decreased interferon-γ levels in steroid naïve asthmatic individuals. Overall, the utilization of EBC solutes as relevant diagnostic markers will rely on the rigorous standardization of sampling procedures.