Seasonal variation and environmental predictors of exhaled nitric oxide in children with asthma

Abstract

SummaryThe fraction of exhaled nitric oxide (FeNO), a measure of airway inflammation, shows promise as a noninvasive tool to guide asthma management, but there is a paucity of longitudinal data about seasonal variation and environmental predictors of FeNO in children. The objective of this project was to evaluate how environmental factors affect FeNO concentrations over a 12-month study period among children with doctor diagnosed asthma. We conducted a prospective cohort study of 225 tobacco-smoke exposed children age 6 to 12 years with doctor-diagnosed asthma including measures of FeNO, medication use, settled indoor allergens (dust mite, cat, dog, and cockroach), and tobacco smoke exposure. Baseline geometric mean FeNO was 12.4 ppb (range 1.9 to 60.9 ppb). In multivariable analyses, higher baseline FeNO levels, atopy, and fall season were associated with increased FeNO levels, measured 6 and 12 months after study initiation, whereas inhaled steroid use, summer season, and increasing nicotine exposure were associated with lower FeNO levels. In secondary analyses of allergen sensitization, only sensitization to dust mite and cat were associated with increased FeNO levels. Our data demonstrate that FeNO levels over a year long period reflected baseline FeNO levels, allergen sensitization, season, and inhaled steroid use in children with asthma. These results indicate that FeNO levels are responsive to common environmental triggers as well as therapy for asthma in children. Clinicians and researchers may need to consider an individual's baseline FeNO levels to manage children with asthma.

Fraction of exhaled nitric oxide measurement as a biomarker in asthma and COPD compared with local and systemic inflammatory markers

“…The current study had evaluated the use of FENO measurement to differentiate between both diseases in comparison with other inflammatory markers. Variables such as sex, current asthma, allergic rhinitis, smoking, current use of inhaled corticosteroids, atopy and seasonality have all been previously identified as important explanatory factors that influence FENO levels [33][34][35][36].…”

Associations of Fraction of Exhaled Nitric Oxide with Beta Agonist Use in Children with Asthma

“…Next, we developed a full multivariable model including environmental, demographic, and treatment covariates determined to be significant in earlier studies. 7,27 We explored interactions of covariates with FeNO levels in these models. A primary interaction of interest was inhaled steroid use as it is associated with FeNO levels and asthma control.…”

“…A primary interaction of interest was inhaled steroid use as it is associated with FeNO levels and asthma control. 9,27 If the interactions were significant, we stratified the model by the interaction variable. After developing these adjusted models, we inserted other clinical measures of asthma status (daily beta agonist use over the previous 2 weeks and unscheduled asthma visits) individually into the models to determine the association of these factors with beta agonist use relative to the FeNO association.…”

Effects of HEPA Air Cleaners on Unscheduled Asthma Visits and Asthma Symptoms for Children Exposed to Secondhand Tobacco Smoke

“…As described previously, exhaled nitric-oxide concentrations were imputed when the exhaled nitric-oxide analysis did not occur within 24 hours after collection. 40 Serum samples were obtained at the baseline visit by a trained pediatric phlebotomist, for determination of allergen-specific immunoglobulin E by using the ImmunoCap test (Pharmacia Diagnostics, Portage, MI). Children with class I or higher immunoglobulin E levels (Ն0.35 kU/L) for dust mite, dog, cat, or cockroach allergen were considered to have atopy.…”