Exhaled breath condensate nitrates, but not nitrites or FENO, relate to asthma control.

BACKGROUND: Asthma is a chronic respiratory disease, characterised by airways inflammation, obstruction and hyperresponsiveness. Asthma control is the goal of asthma treatment, but many patients have sub-optimal control. Exhaled NO and exhaled breath condensate (EBC) NO metabolites (nitrites and nitrates) measurements are non-invasive tools to assess airways inflammation. Our aim was to investigate the relationships between asthma control and the above-named biomarkers of airways inflammation. METHODS: Thirty-nine non-smoking asthmatic patients (19 women) aged 50 (21-80) years performed measurements of exhaled NO (FENO), EBC nitrates, nitrites and pH, and answered Asthma Control Questionnaire (ACQ) and Asthma Control Test (ACT)-questionnaire. RESULTS: The ACT and ACQ score were strongly interrelated (ρ=-0.84, p<0.001). No relationships between ACT or ACQ score and FENO were found (p>0.05). EBC nitrates were negatively related to ACT score (ρ=-0.34, p=0.03) and positively related to ACQ score (ρ=0.41, p=0.001) while no relation of EBC nitrites to either ACQ or ACT score was found (p>0.05). CONCLUSION: EBC nitrates were the only biomarker that was significantly related to asthma control. This suggests that nitrates, but not nitrites or FENO, reflect an aspect of airways inflammation that is closer related to asthma symptoms. Therefore there is a potential role for EBC nitrates in objective assessment of asthma control.