title: The effect of cigarette smoking on exhaled nitric oxide in mild steroid-naive asthmatics.
abstract: OBJECTIVE
  It has been demonstrated previously that exhaled nitric oxide (eNO) is increased in steroid-naive asthmatics and that inhaled steroids reduce eNO in these patients. Cigarette smoking has also been reported to reduce the eNO in healthy volunteers. Recently a correlation has been demonstrated between eNO and airway hyperresponsiveness in steroid-naive, mild asthmatics. We hypothesized that cigarette smoking would reduce the eNO level in steroid-naive asthmatics and might, therefore, affect the correlation between eNO and airway hyperresponsiveness.
  
  
  METHODS
  Comparison of eNO in healthy smoking and nonsmoking volunteers with the level of eNO in steroid-naive and steroid-treated asthmatics. Correlate the eNO level with the provocative concentration of histamine causing a 20% fall in FEV1 (PC20hist) in the asthmatic smoking and nonsmoking patients.
  
  
  METHODS
  University outpatient asthma clinic.
  
  
  METHODS
  eNO levels and PC20hist were measured in three different asthmatic patient groups (group A = 29 steroid-naive, nonsmoking asthmatics; group B = 19 steroid-treated, nonsmoking asthmatics; and group C = 13 smoking, steroid-naive asthmatics) and in two healthy volunteer groups (group D = 18 nonsmoking; and group E = 16 smoking).
  
  
  RESULTS
  eNO in group A was significantly increased compared with the values in groups B and D (21.8+/-12.7, 12.8+/-4.9, and 10.6+/-2.2 parts per billion [ppb], respectively). Cigarette smoking decreased eNO in healthy volunteers (7.4+/-1.8 ppb, group E) as well as in steroid-naive asthmatics (12.7+/-5.1 ppb, group C). There was a significant correlation between eNO and PC20hist in group A (r = -0.45, p < 0.05); this correlation was, however, lost in both groups B and C.
  
  
  CONCLUSIONS
  Cigarette smoking and inhaled steroids reduce the eNO in patients with mild asthma to a comparable extent. Because the correlation between eNO and airway hyperresponsiveness was lost in steroid-treated and smoking, steroid-naive asthmatics, we question the value of eNO as a marker of airway inflammation, at least in mild asthmatics who are already being treated with inhaled steroids or who are currently smoking.
authors.affiliation: Department of Respiratory Diseases, University Hospital Gasthuisberg, Leuven, Belgium. geert.verleden@uz.kuleuven.ac.be
authors.forename: G M
authors.initials: GM
authors.lastname: Verleden
authors.forename: L J
authors.initials: LJ
authors.lastname: Dupont
authors.forename: A C
authors.initials: AC
authors.lastname: Verpeut
authors.forename: M G
authors.initials: MG
authors.lastname: Demedts
mesh_terms: D000280:Administration, Inhalation; D000328:Adult; D000893:Anti-Inflammatory Agents / Q000627:therapeutic use; D001249:Asthma / Q000188:drug therapy / Q000503:physiopathology*; D001507:Beclomethasone / Q000627:therapeutic use; D016535:Bronchial Hyperreactivity / Q000503:physiopathology*; D016022:Case-Control Studies; D005260:Female; D005938:Glucocorticoids / Q000627:therapeutic use; D006801:Humans; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism*; D012907:Smoking / Q000009:adverse effects*
chemical_list: D000893:Anti-Inflammatory Agents; D005938:Glucocorticoids; D009569:Nitric Oxide; D001507:Beclomethasone