Extremely High Fractional Exhaled Nitric Oxide Levels: Impact and Significance in Asthma Management

Background: Fractional Exhaled Nitric Oxide (FeNO) is a biomarker for eosinophilic inflammation used for diagnosis and monitoring of asthma. High FeNO is likely to indicate significant airway eosinophilia and steroid-responsive airway inflammation. However, correlation between abnormally high FeNO levels and disease manifestations is not well established. Our aim was to investigate a possible correlation between high FeNO levels and clinical phenotype, comorbidity and pulmonary function tests (PFT) among asthma patients.

Methods: Data including anthropometric data, symptoms, controller/reliever treatment, comorbidity, PFT was collected for all patients with abnormal FeNO defined as > 35 parts per billions (ppb). We than examined the association between FeNO level and these parameters.

Results: Data was collected from 144 children and adolescents ages 5-18 years. A significant positive association was found between FeNO levels and severe day-time symptoms and poorly controlled asthma (P=0.011, P=0.001, respectively). Patients with FeNO levels of > 80 ppb had more severe day-time symptoms and poorly controlled asthma (P=0.043, P=0.001, respectively) as compared to patients with FeNO < 80 ppb.

Conclusion: High FeNO levels are associated with worst asthma control. FeNO levels > 80 ppb may serve as an objective indicator for severity. These findings may aid in clinical assessment and personalized treatment of asthma patients.