The use of exhaled nitric oxide concentration to identify eosinophilic airway inflammation: an observational study in adults with asthma
Article first published online: 14 SEP 2005
Clinical & Experimental Allergy
Volume 35, Issue 9, pages 1175–1179, September 2005
How to Cite
Berry, M. A., Shaw, D. E., Green, R. H., Brightling, C. E., Wardlaw, A. J. and Pavord, I. D. (2005), The use of exhaled nitric oxide concentration to identify eosinophilic airway inflammation: an observational study in adults with asthma. Clinical & Experimental Allergy, 35: 1175–1179. doi: 10.1111/j.1365-2222.2005.02314.x
- Issue published online: 14 SEP 2005
- Article first published online: 14 SEP 2005
- Submitted 14 December 2004; revised 7 February 2005; accepted 26 June 2005
- nitric oxide
Background Assessment of eosinophilic airway inflammation may be helpful in the management of asthma. Nitric oxide (NO) has potential advantages as a tool to monitor airway inflammation although little is known about the relationship between NO and eosinophilic airway inflammation and the factors which influence it.
Methods We set out to define the relationship between exhaled NO and the sputum eosinophil count, identify the exhaled NO concentration that best identified a sputum eosinophil count >3% and investigate the impact of several potential confounding factors in 566 consecutive patients with varying severity of asthma. Finally we examined the ability of exhaled NO concentrations measured at differing exhalation flows to identify the presence of a sputum eosinophilia.
Results We found a significant positive relationship between exhaled NO and sputum eosinophil count (R2=0.26, P<0.001) which was best described using a non-linear model. There were no clinically important confounding factors to this model. In non-smokers an exhaled NO concentration of >8.3 p.p.b. at 250 mL/s gave 71% sensitivity and 72% specificity for identifying a sputum eosinophil count of >3%.
Conclusions This value of exhaled NO would seem to be the best for identifying significant eosinophilic airway inflammation. It is applicable to a wide range of non-smoking patients with asthma; exhalation flow does not alter the ability of exhaled NO concentration to detect a sputum eosinophilia.