Effect of elevated exhaled nitric oxide levels on the risk of respiratory tract illness in preschool-aged children with moderate-to-severe intermittent wheezing

Abstract

The fractional concentration of exhaled nitric oxide (FeNO) is a noninvasive marker for airway inflammation but requires further study in preschool-aged children to determine its clinical relevance. To determine whether the risk of respiratory tract illnesses (RTIs), disease burden, and atopic features are related to FeNO in preschool-aged children with moderate-to-severe intermittent wheezing. We determined FeNO using the off-line tidal breathing technique in 89 children, aged 12 to 59 months, with moderate-to-severe intermittent wheezing. The risk of RTI was determined by comparing participants with a baseline FeNO of greater than the 75th percentile (24.4 ppb) with those with a baseline FeNO at the 75th percentile or lower using Cox regression analysis. The risk of RTI was significantly higher in children with an FeNO of greater than 24.4 ppb relative to those with lower FeNO values (adjusted relative risk, 3.80; 95% confidence interval, 1.74-8.22; P < .001). FeNO levels of greater than 24.4 ppb were associated with more positive skin test results to aeroallergens (P = .03) but not with other atopic characteristics or historic parameters of illness burden. An elevated FeNO in preschool-aged children with moderate-to-severe intermittent wheezing was associated with an increased risk of RTI during a 1-year follow-up. In addition, a higher FeNO was associated with aeroallergen sensitization.