Abstract
Rationale: Elevated fractional exhaled nitric oxide (FeNO) and bronchial hyperresponsiveness are used as surrogate markers of asthma.
Objective: To investigate the association between FeNO and bronchial responsiveness in a population of high risk children including the full spectrum from asymptomatic children to children with intermittent asthmatic symptoms and children with persistent asthma.
Methods: An unselected group of 196 six-year-old children were included from the Copenhagen Prospective Study on Asthma in Childhood (COPSAC) birth cohort born of mothers with asthma. Bronchial responsiveness was assessed as the relative change in specific airway resistance after cold dry air hyperventilation. FeNO measurements were performed prior to the hyperventilation test. The association between FeNO and bronchial responsiveness was assessed by generalized linear models.
Measurements and main results: Bronchial responsiveness and FeNO exhibited a significant and linear association. A doubling of FeNO corresponded to an 8.4% increase in airway resistance after challenge (95% CI; 3.7-13.1; p=0.0006). There was no evidence of interaction with current asthma and stratified analyses showed similar associations in children with and without asthma.
Conclusion: FeNO and bronchial responsiveness are associated and continuous traits in the population regardless of asthma. This suggests bronchial inflammation may be present subclinically, and cautions against the use of these surrogate markers for a dichotomized approach to asthma diagnosis. Childhood asthma remains a clinical diagnosis and surrogate markers may only be used cautiously as supportive evidence.
- © 2011 ERS
