Association of longitudinal fractional exhaled nitric oxide measurements with asthma control in atopic children.

OBJECTIVES: We sought to determine whether longitudinal measurements of FeNO are informative for future loss of asthma control in children with atopic asthma. METHODS: One hundred seventy-eight patients aged 8-16 years with atopic asthma were enrolled. FeNO and lung functions were serially monitored 10 times or more over 2 years when subjects were not receiving controller medications. After completion of monitoring, 1-year observation on the occurrence of loss of asthma control was performed and associations of loss of asthma control with spirometric and FeNO measurements were analyzed. RESULTS: Loss of asthma control occurred during observation periods in 110 (76%) of 145 patients who completed the study. Of all monitored parameters including airway reactivity, the highest FeNO of serial measurements (H-FeNO) (adjusted odds ratio (aOR), 1.21; 95% CI, 1.08-1.36) and the rate of FeNO levels higher than 21 ppb (R21FeNO) (aOR, 1.06; 95% CI, 1.01-1.11) were the only independent predictors of upcoming control loss in the multiple logistic regression analysis. In receiver-operator characteristic curve analysis, H-FeNO > 37 ppb and R21FeNO > 20% demonstrated 91% and 88% sensitivity for a future loss of asthma control at the cost of low specificity (60% and 65%, respectively). In contrast, H-FeNO > 47 ppb and R21FeNO > 41% gave 96% and 88% specificity, but these sacrificed sensitivity to 70% and 72%, respectively. CONCLUSIONS: Our data show that both amount and frequency of a FeNO increase during longitudinal monitoring are helpful in predicting asthma control status.