The clinical role of fractional exhaled nitric oxide in asthma control.

BACKGROUND: The potential role and characteristics of fractional exhaled nitric oxide (FeNO) remain unclear in the treatment of asthma.

OBJECTIVE: To explore the clinical role of FeNO in asthmatic treatment.

METHODS: We evaluated whether the mean or change of FeNO levels in the treatment period is associated with other conventional control parameters and predicted some clinical outcomes of asthma. We retrospectively analyzed the mean and percentage change of FeNO levels in the first 5 measurements at our hospital.

RESULTS: The study found a significantly strong correlation between FeNO level at diagnosis and the largest changes of FeNO values from diagnosis. No significant correlations were observed between FeNO levels and other parameters (Asthma Control Test [ACT] score or forced expiratory volume in one second [FEV1 ]) in mean and percentage change of values under treatment of asthma; however, significant positive correlations were found between ACT scores and FEV1 . The mean FeNO level revealed a significant negative correlation with an annual change in FEV1 in individuals with asthma who were followed up for more than 2 years. Both the mean ACT score and percent predicted FEV1 revealed a significant negative correlation with occasional use of systemic corticosteroids.

CONCLUSION: During conventional treatment of asthma, the largest changes of FeNO values from diagnosis were strongly correlated with FeNO levels at diagnosis. As for the unlikely conventional parameters, no significant associations were observed between FeNO levels and deterioration of asthma during the treatment periods. An elevated mean FeNO level may be a marker of decreased lung function in individuals with asthma.