Exhaled nitric oxide - Is it really a good marker of airway inflammation in bronchial asthma?

Background: The concentration of exhaled nitric oxide ([NO]) has been repor ted to reflect the inflammatory process of airways in patients with bronchi al asthma, particularly when they are steroid naive. However, it is not ful ly understood whether it equally reflects the degree of airway inflammation in patients receiving inhaled corticosteroids, but whose symptoms are not necessarily well controlled. Objective: To examine whether the exhaled [NO] really reflects airway inflammation in patients with bronchial asthma, reg ardless of treatment with inhaled steroids. Methods: Exhaled [NO] was measu red in patients with bronchial asthma (43 steroid treated and 32 steroid na ive), chronic obstructive pulmonary disease (COPD) (n = 36), bronchiectasis (n = 10) and in control subjects (n = 26). We examined in each asthmatic g roup whether the exhaled [NO] correlated with parameters reflecting airway inflammation. Results: Exhaled [NO] was significantly correlated with sympt om score, clinical severity, circulating eosinophil count, and the percenta ge of eosinophils in induced sputum in the steroid-naive asthmatics, but no t in the steroid-treated asthmatics, although airway inflammation in this g roup was not well controlled, as evidenced by clinical symptoms and the hig her percentage of eosinophils in induced sputum. Exhaled [NO] from the pati ents with COPD (6.2 +/- 0.7 ppb) or bronchiectasis (5.4 +/- 1.3 ppb) was no t significantly increased compared with the controls (6.0 +/- 1.0 ppb), and was significantly lower than in the asthmatic patients as a whole (19.0 +/ - 2.0 ppb). Conclusions: Although exhaled [NO] is a useful marker of airway inflammation for differential diagnosis and evaluation of severity in ster oid-naive patients with bronchial asthma, it may not be as useful in steroi d-treated patients. Copyright (C) 2000 S. Karger AG, Basel.