Abstract
Introduction: Exhaled nitric oxide (FENO) is a biomarker of eosinophilic airway inflammation, but the relationship between FENO and asthma severity is uncertain. We compared FENO normalized against reference values (%FENO) in children with Problematic severe (PA) and controlled (CA) asthma and investigated whether increased %FENO is associated with morbidity, irrespective of predefined severity classification.
Methods: Children with PA had recurrent symptoms despite treatment with ≥800 µg Budesonide, those with CA had few symptoms with 100-400 µg. The protocol included Asthma control test, spirometry (%), methacholine provocation (dose response slope), FENO (p.p.b.), computerized tomography (CT) of the lungs (PA only) and blood sampling for eosinophils (109 x L-1) and IgE (kU/L). The difference between measured and expected FENO (Ln(FENO) = 0.0112 x height (cm) + 0.641) were given in percentages (%FENO).
Results: Children with PA (n=57, age 13y) had a trend towards higher levels of FENO and %FENO compared to children with CA (n=39, age 14y): 22 (10-40) vs. 17 (9-26), p=0.13 and 210% (101-367) vs. 139% (85-216), p=0.07, respectively. When analysing all children (n=96), those with %FENO>200 had reduced asthma control (18.5 (17-20) vs. 20.4 (19-22), p=0.04) and FEV1/FVC (77 (74-81) vs. 83 (81-86), p=0.004) and increased bronchial hyperresponsiveness (54 (5-67) vs. 2 (0.4-36), p=0.001), bronchial wall thickening on CT (25 (21-29) vs. 17 (14-19), p=0.004), eosinophils (0.5 (0.4-0.6) vs. 0.3 (0.2-0.3), p<0.001) and IgE (539 (253-1525) vs. 140 (43-425), p<0.001) compared to those with %FENO<200.
Conclusion: Children with high levels of %FENO have increased morbidity which is partly independent of predefined severity classification.
- © 2012 ERS