2.4 Methods
The diagnosis of the etiology of all children with non-specific chronic cough was referenced to the diagnosis and differential diagnosis of chronic cough in children guidelines[1,5].Each of the patients underwent the following procedures for the investigation of the cause of cough: 1) detailed recording of medical history(duration and nature of the cough, associated symptoms, the history of medication, family history of allergic disease or related disease and information about the living environment of the patient); 2) detailed physical examination with particular attention to the heart and lower and upper airways; and 3) Allergen test, Pulmonary function assessment, chest X-ray examination/further chest computed tomography (CT) examination, nasal endoscopy, bronchoscopy and bronchoalveolar lavage fluid cytology and pathogen isolation and culture or ethacholine-challenge test in patients with suspicious symptoms or signs.