Exhaled nitric oxide: Interactions between asthma, hayfever, and atopic dermatitis in school children

Background: Clinicians frequently rely on reported symptoms and basic pulmonary function testing to assess asthma prevalence in the community However, given that spirometry results are often normal for asthmatic children and the fact that there is no equivalent word for 'wheeze' in languages other than English, the assessment of asthma prevalence can be troublesome. Objective: To evaluate in a population based setting, whether FeNO as a non-invasive marker, contributes to the detection of asthma. Methods: This cross-sectional study was carried out on primary school children from Northern and Southern Tyrol. FeNO measurements were made using the online single breath technique prior to spirometry. Symptom status including asthma, hayfever and atopic dermatitis was determined by the ISAAC questionnaire. Results: Six hundred and forty-four Tyrolean children aged 8-10 years participated. In terms of FEV1, % predicted, the asthma and hayfever group had significantly lower values compared to the asymptomatic group, the hayfever only, and the atopic dermatitis only groups. For FeNO, participants with asthma and hayfever, asthma and atopic dermatitis, and hayfever only recorded significantly greater FeNO values when compared to the asymptomatic group. Moreover, the asthma and atopic dermatitis group recorded significantly greater FeNO when compared to the asthma only group. Multivariate regression revealed that asthma had a small significant inverse association with FEV1, % predicted for the individual model and when combined with hayfever. For FeNO, each of the individual and combined model analyses achieved significance. Conclusion: Although FeNO appears to be influenced by asthma, the presence of other atopic conditions confounds the relationship. Elevated levels of FeNO do not distinguish between asthma and other atopic conditions. Therefore, FeNO does not contribute to the detection of asthma in the community Clinical Implication: FeNO is not a valuable tool for the detection of asthma in the community as it is confounded by other atopic conditions.