Increased exhaled nitrite in children with allergic asthma is not related to nitric oxide formation

Abstract

Nitrite sampled from the upper airways could originate from inflammation-induced nitric oxide (NO), as reports of elevated nitrite in exhaled breath condensate (EBC) from asthmatics suggest, but also through bacterial action in the pharyngo-oral tract. To correlate EBC nitrite and nitrate to exhaled NO (FENO, fraction of expired NO) and other markers of disease activity in children with allergic asthma and thereby further investigate their role and origin. EBC was collected from 27 asthmatic subjects (ages 6-17 years, all immunoglobulin E-positive for aeroallergens) and 21 age-matched non-atopic healthy controls for fluorometric analysis of nitrite and nitrate. These markers were compared with measurements of FENO, blood eosinophil count (EOS), methacholine reactivity (PD(20)) and baseline spirometry. EBC nitrite, in contrast to nitrate, was significantly increased (P < 0.01) in the asthmatic children. They also had increased levels of FENO (P < 0.001) and EOS (P < 0.001) along with decreased PD(20) (P < 0.001) and FEV1/FVC (P < 0.01). However, there was no correlation between EBC nitrite and FENO (r = 0.05) or any other marker of disease activity in the asthmatic children, whereas between the other markers correlations could be established. EBC nitrite is elevated in childhood asthma but the lack of correlation to FENO and other markers, together with simultaneously normal levels of nitrate, make its origin as a metabolite of inflammation-induced NO questionable.