Identifying the predictive value of fractional exhaled nitric oxide (FeNO) for uncontrolled asthma in 3-7-year-old Thai children.

Background: Fractional exhaled nitric oxide (FeNO) is the method for monitoring airway inflammation. However, a singular FeNO value cutoff may not adequately represent the control status across different ages and demographics. This study aimed to evaluate the correlation between FeNO values and asthma control levels, identifying an optimal cutoff point for children aged 3 to 7 years. Methods: This cross-sectional study was conducted at Naresuan University Hospital from April 1, 2023 to July 31, 2023. Inclusion criteria were asthmatic patients aged 3 to 7 years who were capable of following commands. Exclusion criteria included children who had a coronavirus disease 2019 (COVID-19) infection, those experiencing difficulty breathing, or unable to perform the FeNO measurement. Eligible patients were classified according to their level of asthma control and underwent FeNO testing. Results: Out of 108 participants who successfully completed FeNO measurements, a significant difference in FeNO values was observed across controlled, partially controlled, and uncontrolled asthma groups, with uncontrolled asthma presenting significantly higher values. The optimal FeNO cutoff point for predicting uncontrolled asthma was identified as ≥15 ppb with a sensitivity 46.7%, specificity 86.0%, positive predictive value (PPV) 35.0%, negative predictive value (NPV) 90.9%. Conclusions: This study established a significant correlation between FeNO levels and uncontrolled asthma, FeNO cutoff point ≥15 ppb as the optimal value in predicting uncontrolled asthma in Thai children aged 3-7 years. Factors such as uncontrolled allergic rhinitis, symptoms at onset, smoking exposure, treatment compliance, and inhaled corticosteroid (ICS) usage were associated with FeNO values. The application of FeNO measurement should be integrated with clinical assessments and consideration of these associated factors.