Fractional Exhaled Nitric Oxide (FeNO) Integrating Airway Hyperresponsiveness (AHR) Examination Promotes Etiologic Diagnosis and Treatment for Children with Chronic Cough

BACKGROUND: Chronic cough is the main reason why parents seek medical treatment for their children. This study aimed to evaluate changes in airway function and inflammation levels and associated values in diagnosing and treating chronic cough. MATERIAL/METHODS: This study involved 118 children with chronic cough, including 45 cough-variant asthma (CVA) patients, 53 upper-airway cough syndrome (UACS) patients, and 20 post-infection cough (PIC) patients. Chronic cough was diagnosed as described by guidelines of the American College of Chest Physicians for evaluating chronic cough. Pulmonary ventilation function and airway hyperresponsiveness (AHR) were evaluated. Fractional exhaled nitric oxide (FeNO) levels and eosinophilic airway inflammation were measured. Eosinophil (EOS) count in sputum was also examined. CVA patients were treated with inhaled glucocorticoids, which have anti-inflammatory effects. RESULTS: FeNO and sputum EOS levels were higher in CVA patients compared with UACS and PIC patients (P<0.05). CVA patients demonstrated significantly higher small airway indexes, including 25% forced expiratory flow (FEF), 50% FEF, and 75% FEF, compared with UACS and PIC patients (P<0.05). FeNO level was positively correlated with EOS in sputum (r=0.468, P=0.0001) and cough symptom scores (r=0.402, P<0.05). FeNO, EOS, and cough symptoms were significantly improved in CVA patients after glucocorticoid treatment. AHR was improved in all chronic cough patients after treatment. Cough-relief CVA patients demonstrated significantly higher FeNO levels compared with those without cough relief (P<0.05). CONCLUSIONS: FeNO integrating pulmonary function and AHR examination can improve etiologic diagnosis and treatment for chronic cough in children.