Cough variant asthma sputum eosinophil count and exhaled breath nitric oxide (FeNO) levels will be high, and pulmonary function tests suggest small airway dysfunction, elevated airway resistance, and a positive airway provocation test. 1. The pathology of cough variant asthma is characterized by airway eosinophilic inflammation. Eosinophils can be detected in induced sputum, tracheal mucosal biopsy tissues and bronchoalveolar lavage fluid; therefore, sputum eosinophilia is one of the diagnostic indicators of cough variant asthma. 2.FeNO is mainly derived from respiratory epithelial cells, which produce NO by expressing NO synthase induced by inflammatory cytokines.The stimulation of inflammatory factors released by eosinophils can increase FeNO, so FeNO can reflect the degree of eosinophilic inflammatory response. Therefore, FeNO level will be elevated. 3. Lung function test: Early lung function test in patients with cough variant asthma often suggests small airway dysfunction, which may be accompanied by elevated airway resistance, and the condition progresses gradually to typical bronchial asthma, which may appear ventilation dysfunction. 4. Airway provocation test: the diagnostic examination of cough variant asthma, positive airway provocation test can be diagnosed as airway hyperresponsiveness, supporting the diagnosis of cough variant asthma. If the diagnosis of cough variant asthma is confirmed, early and standardized treatment is recommended to reduce the adverse effects of the disease.