Exhaled nitric oxide, sensitization, and exposure to allergens in patientswith asthma who are not taking inhaled steroids

The level of exhaled nitric oxide (eNO) is elevated in patients with asthma and eNO may be involved in airway inflammation. Exposure to allergen in se nsitized individuals may contribute to airway inflammation. Our aim was to investigate the relationship between eNO, sensitization, and exposure to in door allergen in nonsmoking adults with asthma who are not taking inhaled s teroids. In subjects with a positive methacholine challenge (PD20 < 4 mg) w e measured eNO (LR 2000 chemiluminesence analyzer); serum total and specifi c IgE; skin test to mite, cat, and dog; and allergen levels in domestic dus t (Derp 1, Fel d 1, and Can f 1). Subjects were classified as exposed or no t exposed to allergen according to previously proposed significant levels ( > 2 mu g/g Der p 1, > 8 mu g/g Fel d 1, and > 10 mu g/g Can f 1). Of the 43 subjects (> 95% atopic) complete data were available for 38, of whom 26 we re both sensitized and exposed to one or more allergen and 12 were sensitiz ed but not exposed to any allergens. eNO was significantly higher in those subjects who were both sensitized and exposed to indoor allergen than in th ose who were sensitized but not exposed (CM and 95% CI: 17.69 [14.1-22.15] versus 9.09 [6.5-12.7], p = 0.001). Levels of eNO are significantly higher in patients with asthma who are both sensitized and exposed to relevant all ergen than in those who were sensitized but not exposed. eNO may be a marke r of the airway inflammation induced by domestic exposure to allergen in se nsitized patients with asthma.