Exhaled nitric oxide predicts airway hyper‐responsiveness to hypertonic saline in children that wheeze

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Abstract
Background:  Exhaled nitric oxide (eNO) has shown good validity for the assessment of airway inflammation in asthmatic children. In large‐scale epidemiological studies, this method would be preferred above airway challenge tests, because it is a quick and easy applicable tool.Objective:  In this study, we aimed to assess the discriminatory capacity of eNO, and prechallenge FEV1 for airway hyper‐responsiveness (AHR) in 8–13‐year old schoolchildren.Materials and methods:  Parents completed the ISAAC questionnaire, and children were tested for atopy, AHR to hypertonic (4.5%) saline (HS), and eNO. Diagnostic value was assessed by the area under the receiver operating curves (ROC), and calculation of positive and negative predicted values at different cut‐off points for eNO and prechallenge FEV1.Results:  Areas under the ROC‐curves of AHR were 0.65 for eNO and 0.62 for FEV1. Values increased to 0.71 and respectively 0.75 for a combined occurrence of AHR and current wheeze. Highest sensitivity and specificity were obtained at a cut‐off value of 43 ppb for eNO and 103% predicted for FEV1. At these cut‐off values, the positive predictive values for the presence of AHR in symptomatic children were respectively 83% (eNO) and 33% (FEV1), and negative predictive values in asymptomatic children were, respectively, 90 (eNO) and 80% (FEV1).Conclusion:  Exhaled nitric oxide is a valid screening tool for AHR to HS in children that present with current wheeze, and it outperforms FEV1 as a predictor of AHR.