Do levels of exhaled nitric oxide reflect bronchial inflammation and peripheral blood eos1nophilia in inhaled corticosteroid-treated and untreated adult asthmatic patients?

Background Assessment of exhaled nitric oxide (eNO) levels and sputum eosinophils (EO) have been used as non-invasive surrogates of airway inflammation in mild asthma. However, their utility in monitoring airway inflammation in asthmatics with more severe disease treated with moderate doses of inhaled corticosteroid (ICS)-treated is uncertain. Methods We determined eNO in 55 stable but symptomatic asthmatic subjects (26 using i-agonists alone = group I, and 29 using at least 1000 |jg/day of inhaled beclomethasone or equivalent = group II) and assessed its relationship to sputum and peripheral blood EO, and bronchial hyper-responsiveness (BHR) as measured by PDiQ methacholine. Comparative eNO data was obtained from 40 non-smoking, normal subjects. Results Exhaled NO levels were significantly higher in group 1 (median 33.5 ppb, range 9-77 ppb) compared to group II subjects (median 14 ppb. range 8-34 ppb, p0.005) and normal controls (median 15 ppb. range 10-25 ppb. p0.0001 ). Sputum and blood EO and BHR did not differ between asthmatic groups. Exhaled NO was related to sputum EO in group I subjects only (r(sl=0.6, p0.05, cf group II; r(s,0.2, p0.4). Sputum and blood EO were significantly related in both groups I and II (r(sl=0.8. r(sl=0.8 respectively, p0.005) and eNO levels also correlated with peripheral blood EO in each group (r(S)=0.6. r(S|=0.5 respectively.