Raised FeNO is associated with lower FEV1 and FEV1/FVC in children with asthma

Introduction: The relationship between airway inflammation and decline in lung function is not well understood. Previous studies have not consistently demonstrated correlation between FeNO and a commonly used spirometric parameter - FEV1 % predicted (Spergel et al. J Asthma 2005;42:879-883; Stanciulescu et al. Pneumologia 2015;64:40-44). Objective: To describe the relationship between FeNO and spirometry in children managed for asthma, using gold standard GLI reference equations and z-scores for FEV1 and FEV1/FVC. Methods: Cross-sectional observational study conducted in UK primary care. Children (5-16yr) with asthma or on asthma medication were invited for a spirometry and FeNO test. Absolute values for FEV1 and FEV1/FVC were converted into Z-scores using the GLI-2012 calculator. Results: Spirometry and FeNO were obtained in 465 children. Of these, 232 (50%) had at least one abnormal test result. Fifty-two (11%) children had obstructed spirometry but normal FeNO, 111 (24%) had raised FeNO ≥ 35ppb only, and 58 (12%) had both obstructed spirometry and raised FeNO. We found a significant but weak negative correlation between both FEV1 and FEV1/FVC with FeNO (Fig 1). Conclusion: Raised FeNO was associated with lower FEV1 and FEV1/FVC. Causality cannot be concluded from this observational study. Longitudinal studies are required to investigate whether a link exists between airway inflammation and more rapidly declining lung function.