Increase in exhaled nitric oxide levels in patients withdifficult asthma and correlation with symptoms and disease severitydespite treatment with oral and inhaled corticosteroids

摘要

BACKGROUND—Patients with difficult asthma suffer chronic moderate to severe persistent asthma symptoms despite high doses of inhaled and oral corticosteroid therapy. These patients suffer a high level of treatment and disease related morbidity but little is known about the degree of airway inflammation in these patients.
METHODS—Fifty two patients were examined to assess levels of exhaled nitric oxide (NO) as a surrogate marker of inflammatory activity in this condition. From this group, 26 patients were defined with severe symptoms and current physiological evidence of reversible airway obstruction requiring high dose inhaled (⩾2000 µg beclomethasone dipropionate (BDP) equivalent) or oral steroid therapy to maintain disease control.
RESULTS—Exhaled NO levels were higher in subjects with difficult asthma (mean 13.9 ppb, 95% CI 9.3 to 18.5) than in normal controls (7.4 ppb, 95% CI 6.9 to 7.8; p<0.002), but lower than levels in steroid naive mild asthmatics (36.9 ppb, 95% CI 34.6 to 39.3; p<0.001). Prednisolone treated patients had higher exhaled NO levels than patients only requiring inhaled corticosteroids (17.5ppb, 95% CI 11.1 to 24.0 versus 7.2 ppb, 95% CI 4.6 to 9.8; p= 0.016), suggesting greater disease severity in this group. Non-compliance with prednisolone treatment was observed in 20% of patients but this didnot explain the difference between the treatment groups. Exhaled NOlevels were closely correlated with symptom frequency (p = 0.03) andwith rescue β agonist use (p<0.002), but they did not correlate withlung function.
CONCLUSIONS—Exhaled NO may serve as a usefulcomplement to lung function and symptomatology in the assessment ofpatients with chronic severe asthma, and in the control andrationalisation of steroid therapy in these patients.