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 reported to reflect the inflammatory process of airways in patients with bronchial asthma, particularly when they are steroid naive. However, it is not fully 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, regardless of treatment with inhaled steroids.


METHODS
Exhaled [NO] was measured in patients with bronchial asthma (43 steroid treated and 32 steroid naive), chronic obstructive pulmonary disease (COPD) (n = 36), bronchiectasis (n = 10) and in control subjects (n = 26). We examined in each asthmatic group whether the exhaled [NO] correlated with parameters reflecting airway inflammation.


RESULTS
Exhaled [NO] was significantly correlated with symptom score, clinical severity, circulating eosinophil count, and the percentage of eosinophils in induced sputum in the steroid-naive asthmatics, but not in the steroid-treated asthmatics, although airway inflammation in this group was not well controlled, as evidenced by clinical symptoms and the higher percentage of eosinophils in induced sputum. Exhaled [NO] from the patients with COPD (6.2 +/- 0. 7 ppb) or bronchiectasis (5.4 +/- 1.3 ppb) was not 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 steroid-naive patients with bronchial asthma, it may not be as useful in steroid-treated patients.
Tsujino
I
I
First Department of Medicine, Hokkaido University, School of Medicine, Sapporo, Japan. it013@med.hokudai.ac.jp
Nishimura
M
M
Kamachi
A
A
Makita
H
H
Munakata
M
M
Miyamoto
K
K
Kawakami
Y
Y
D000305:Adrenal Cortex Hormones / Q000008:administration & dosage; D000328:Adult; D000368:Aged; D001249:Asthma / Q000175:diagnosis* / Q000188:drug therapy / Q000378:metabolism*; D015415:Biomarkers / Q000032:analysis; D001944:Breath Tests; D001987:Bronchiectasis / Q000175:diagnosis / Q000378:metabolism; D001993:Bronchodilator Agents / Q000008:administration & dosage; D016022:Case-Control Studies; D003937:Diagnosis, Differential; D004804:Eosinophils; D005260:Female; D006801:Humans; D007249:Inflammation; D008173:Lung Diseases, Obstructive / Q000175:diagnosis / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D009569:Nitric Oxide / Q000378:metabolism*; D012141:Respiratory Tract Infections / Q000175:diagnosis / Q000378:metabolism; D013183:Sputum
D000305:Adrenal Cortex Hormones; D015415:Biomarkers; D001993:Bronchodilator Agents; D009569:Nitric Oxide