Association between levels of fractional exhaled nitric oxide and asthma exacerbations in Thai children.

BACKGROUND AND OBJECTIVE: Fractional exhaled nitric oxide (FeNO) has been used as a marker for airway inflammation. We evaluated the association between FeNO levels and asthma exacerbations (AEs) in Thai children and young adults.

METHODS: This was a prospective cohort study in patients with atopic asthma aged 7-20 years. Asthma control level and management were evaluated every 3 months for 1 year. Spirometry and FeNO measurements were performed at baseline, and 6 and 12 months.

RESULTS: In all, 70 patients (median age: 12.6 (7.2-19.8) years) were enrolled, of whom 18% had an AE during the study period. Median FeNO levels were significantly higher in patients with an AE than in those without an AE (35.6 ppb vs 16.5 ppb; P = 0.012). FeNO of 31 ppb provided optimal sensitivity (92.3%) and specificity (75.4%) for AE prediction. Sensitivity and specificity of FeNO levels were higher than those of forced expiratory volume in 1 s and forced expiratory flow at 25-75% of forced vital capacity bronchodilator reversibility for the prediction of an AE, but the difference was not significant (P = 0.121). None of the patients with FeNO level of 0-20 ppb had an AE within 12 months. Percentage of patients with FeNO of 21-40 ppb who suffered an AE was 20% and 30% at 6 and 12 months, respectively.

CONCLUSION: The optimal cut-off point of FeNO level for the prediction of AE is 31 ppb. AE within the next 12 months was significantly more common in patients with higher FeNO levels and in patients with a higher rate of previous 12-month exacerbations.