Exhaled nitric oxide in school children: Searching for the lost variability

ObjectiveThe factors – including asthma and rhinoconjunctivitis – which influence FeNO values in a general population of school children have been studied in order to know to what extent the variability of those values can be explained.MethodsFeNO was measured in a population of 240 school children aged 6–12 years by means of a Niox-Mino™ device in a standardised way. Parents filled in an ISAAC-validated questionnaire of symptoms and environmental factors. Diagnoses were checked against clinical records. Height and weight were measured. A multivariate regression analysis including all variables in the questionnaire was performed, which was followed by two Xi stepwise tests in order to build a predictive model which included the main variables influencing FeNO values.ResultsAmong the 240 children, 10 suffered from asthma, 16 from rhinoconjunctivitis and 15 from both conditions. FeNO values (GM ± GSD) in children with rhinoconjunctivitis (19.61 ± 1.20 ppb), with asthma (18.62 ± 1.32 ppb), and with both conditions (17.62 ± 1.19 ppb) tended to be significantly higher than control children (11.42 ± 1.04 ppb), p = 0.0016, p = 0.08 and p = 0.01, respectively. The different predictive models were able to explain only 20–27% of FeNO variability.ConclusionsThe proportion of FeNO inter-individual variability which can be explained by individual (including suffering from asthma or rhinoconjunctivitis), family, and environmental factors is very low (20–27%). This could have implications on the usefulness of FeNO as a diagnostic tool in asthma.