2009 Jun - Determinants and Reference Values for Fraction of Exhaled Nitric Oxide (FENO) in Healthy, Non-smoking Chinese Adults
Dr Alvin Tung, Department of Medicine & Therapeutics, Prince of Wales Hospital
Background:
The measurement of Fraction of Exhaled Nitric Oxide (FENO) has been proposed as a marker that can aid the diagnosis and management of airway diseases. There have been many studies investigating the various determinants that affect FENO in different races and subsets of population, but few were performed in healthy, non-smoking Chinese population. No data on its reference values was available locally. The study aimed to investigate the determinants and reference values for FENO in non-smoking Chinese adults.
Methods:
Five hundred and thirty six subjects (n=536), being either staff, co-workers or medical students of a local university teaching hospital were recruited between January 2007-June 2008 for this cross-sectional study. Current smokers and ex-smokers were excluded. Assessments included measurement of the FENO level, spirometry, anthropometric variables, total serum immunoglobin E (IgE) levels and eosinophil count in peripheral blood, In addition, the presence of atopy was assessed by skin prick test and rhinitis symptoms by history. The associations between FENO and different determinants were analysed by Spearman’s correlation test and multiple linear regression models. The predictors and reference values for FENO were calculated.
Results:
The mean FENO level was 35.2 parts per billion (ppb) (SD 27.6), ranging from 1.35 to 215 ppb. Height (r=0.244, p=<0.001), weight (r=0.223, p<0.001), pre- and post-bronchodilator FEV1 (r=0.201, p<0.001 and r=0.203 p<0.001), peripheral blood eosinophil count (r=0.300, p<0.001) and total IgE level (r=0.317, p<0.001) were all positively associated with FENO. Males, subjects with allergic rhinitis or atopy had a higher mean FENO than their respective counterparts. Multiple stepwise regression analysis showed that significant predictors of FENO were sex (β=-0.181, p<0.001), allergic rhinitis (β=0.248, p<0.001), total IgE level (β= 0.102, p=0.01) and peripheral blood eosinophil count (β= 0.249, p<0.001). The 95% upper limit of FENO in men and women were 110.85 ppb and 78.77 ppb respectively. For males with rhinitis and without rhinitis, the 95% upper limits were 164.50 and 74.26 ppb respectively. For females with and without rhinitis, the 95% upper limits were 117.25 and 53.04 ppb respectively.
Conclusion:
In this random healthy, non-smoking Chinese population, sex, allergic rhinitis, total serum IgE level and peripheral blood eosinophil count were significant predictors of FENO. The 95% reference values of FENO in men and women may serve as a guide in the diagnosis and management of airway diseases.
