OBJECTIVETo study the diagnostic values of fractional exhaled nitric oxide (FeNO) for typical bronchial asthma and cough variant asthma in children, and to explore whether FeNO can be applied to differentiate typical bronchial asthma from cough variant asthma in children.

METHODSA total of 150 children who were newly diagnosed with typical bronchial asthma between June 2012 and June 2014, as well as 120 children who were newly diagnosed with cough variant asthma during the same period, were selected as subjects. FeNO measurement, spirometry, and methacholine provocation test were performed for both groups. Meanwhile, 150 healthy children were selected as the control group, and their FeNO was measured. The diagnostic values of FeNO for typical bronchial asthma and cough variant asthma were analyzed using the receiver operating characteristic curve.

RESULTSThe FeNO values in the typical bronchial asthma and cough variant asthma groups were significantly higher than in the control group (P<0.01), and the FeNO value in the typical bronchial asthma group was significantly higher than in the cough variant asthma group (P<0.01). FEV1/FVC%, FEV1%pred, and PD20 were significantly lower in the typical bronchial asthma group than in the cough variant asthma group (P<0.01). The optimal cut-off value of FeNO was 19.5 ppb for the diagnosis of typical bronchial asthma, with a sensitivity of 83.3% and a specificity of 86.7%; the optimal cut-off value of FeNO was 15.5 ppb for the diagnosis of cough variant asthma, with a sensitivity of 67.5% and a specificity of 78.0%; the optimal cut-off value of FeNO was 28.5 ppb for the differentiation between typical bronchial asthma and cough variant asthma, with a sensitivity of 60.7% and a specificity of 82.5%.

CONCLUSIONSMeasurenment of FeNO may be useful in the diagnosis and differential diagnosis of typical bronchial asthma and cough variant asthma.