Combined prediction of fractional exhaled nitric oxide and pulmonary function tests for airway hyperresponsiveness in children with chronic cough.

Background: Coughing, as one of the most common symptoms of the respiratory system in children, has a variety of etiologies. This study aimed to explore the predictive value of fractional exhaled nitric oxide (FeNO) combined with pulmonary ventilation function tests for airway hyperresponsiveness (AHR) in children with chronic cough.

Methods: A total of 157 children with chronic cough who visited Chengdu Women and Children's Central Hospital from January 2020 to January 2024 were included. They were divided into a positive bronchial provocation test group (n=69) and a negative bronchial provocation test group (n=88) based on the results of the bronchial provocation test. The pulmonary ventilation function parameters and FeNO levels of the two groups were compared, and the predictive value of each index for AHR was evaluated through the receiver operating characteristic (ROC) curve.

Results: The forced expiratory volume in the first second (FEV1), FEV1/forced vital capacity (FVC), forced expiratory flow at 25% of FVC exhaled (FEF25), forced expiratory flow at 50% of FVC exhaled (FEF50), forced expiratory flow at 75% of FVC exhaled (FEF75), and maximum mid-expiratory flow (MMEF) of the positive provocation group were significantly lower than those of the negative provocation group, and the FeNO level was significantly higher, with statistically significant differences (P<0.05). Further analysis through the ROC curve revealed that MMEF had the highest predictive efficacy for AHR [area under the curve (AUC) =0.88, 95% confidence interval (CI): 0.82-0.94]; when FeNO was combined with pulmonary ventilation function parameters, the combination of MMEF and FeNO had the best predictive efficacy (AUC =0.91, 95% CI: 0.86-0.96), with optimal cut-off values of 67.05% and 20.50 ppb.

Conclusions: The combination of FeNO and MMEF can effectively predict AHR in children with chronic cough and has significant clinical value for the differential diagnosis of chronic cough etiology.