Abstract
BackgroundExhaled nitric oxide (FENO) measurements are used as a surrogate marker for eosinophilic airway inflammation. However, many constitutional and environmental factors affect FENO, making it difficult to devise reference values. Our aim was to evaluate the relative importance of factors affecting FENO in a well characterised adult population.MethodsData were obtained from 895 members of the Dunedin Multidisciplinary Health and Development Study at age 32. The effects of sex, height, weight, lung function indices, smoking, atopy, asthma and rhinitis on FENO were explored by unadjusted and adjusted linear regression analyses.ResultsThe effect of sex on FENO was both statistically and clinically significant, with FENO levels approximately 25% less in females. Overall, current smoking reduced FENO up to 50%, but this effect occurred predominantly in those who smoked on the day of the FENO measurement. Atopy increased FENO by 60%. The sex-related differences in FENO remained significant (p < 0.001) after controlling for all other significant factors affecting FENO.ConclusionEven after adjustment, FENO values are significantly different in males and females. The derivation of reference values and the interpretation of FENO in the clinical setting should be stratified by sex. Other common factors such as current smoking and atopy also require to be taken into account.
Highlights
Exhaled nitric oxide (FENO) measurements are used as a surrogate marker for eosinophilic airway inflammation
Respiratory Research 2007, 8:82 http://respiratory-research.com/content/8/1/82 assessments of airway pathology such as induced sputum, [2,3] bronchial lavage fluid, [4] or mucosal biopsy. [5,6,7] Against this background, factor determining exhaled nitric oxide (FENO) measurements are increasingly being used to clarify the aetiology of non-specific respiratory symptoms as well as monitor levels of inflammation in conditions characterised by airway eosinophilia [8]
FENO was on average 25% higher in males than females
Summary
Exhaled nitric oxide (FENO) measurements are used as a surrogate marker for eosinophilic airway inflammation. Many constitutional and environmental factors affect FENO, making it difficult to devise reference values. Our aim was to evaluate the relative importance of factors affecting FENO in a well characterised adult population. Measurement of exhaled nitric oxide (FENO) is increasingly recognised as an important addition to pulmonary function testing in clinical practice [1]. [5,6,7] Against this background, FENO measurements are increasingly being used to clarify the aetiology of non-specific respiratory symptoms as well as monitor levels of inflammation in conditions characterised by airway eosinophilia [8]. Buchvald et al have reported reference values in a large population of children, but important biological confounders were evaluated only by questionnaire. In the present study, comprising a well characterised cohort of nearly 1000 32-year old individuals born in Dunedin, New Zealand, we obtained detailed clinical and laboratory information regarding factors affecting FENO, and their potential relevance to reference ranges for FENO was evaluated
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