OBJECTIVETo study the utility of fractional exhaled nitric oxide (FeNO) in young children at different stages of asthma.

METHODSFifty-eight children with newly diagnosed asthma (aged 1-3 years) at the acute exacerbation stage between April and June, 2014 were recruited. After 3 months' treatment, the children switched into the chronic persistent stage (n=34) or remission stage (n=24). Thirty aged-matched healthy children served as controls. FeNO levels and lung function were measured for all subjects. The best cut-off value of FeNO for the diagnosis of asthma was evaluated by receiver operating characteristic (ROC) curve.

RESULTSThe FeNO levels in children with asthma at various stages were higher than controls (P<0.05). The FeNO levels in the acute exacerbation stage were highest, followed by the chronic persistent stage (P<0.05). FeNO level was correlated to the stages of asthma (r=-0.382, P<0.001). The cut-off value of FeNO for the diagnosis of asthma was 22.75 ppb by ROC curve, with the sensitivity of 0.933 and the specificity of 0.388.

CONCLUSIONSThe children with asthma at different stages have different FeNO levels. Measurement of FeNO is useful in the diagnosis of asthma in young children.