To investigate the value of blood eosinophils, FeNO and total IgE in predicting the response to inhaled corticosteroid in patients with chronic cough.

Chronic cough is a frequent complaint in respiratory specialists clinic. CVA, UACS, EB, GERC and AC are common causes of chronic cough, among whom, CVA, EB and AC can be classified as corticosteroid responsive cough.

To recognize the eosinophilic airway inflammation and assess the response of inhaled corticosteroid, induced sputum analysis is the most widely used examination but not all the subjects can provide an suitable sample of sputum for measurements and it's time-consuming.

Recently, blood eosinophils, FeNO and total IgE were detected to be biomarkers of eosinophilic airway inflammation for asthmatics. However, whether can they predict the response to corticosteroid in chronic cough remains uncertain.

The present prospective, multi-center, randomized placebo-controlled study aims to explore the value of blood eosinophils, FeNO and total IgE in predicting the response to inhaled corticosteroid in patients with chronic cough.

Inclusion Criteria:

1. Age: 18-70 years;
2. Coughing lasting ≥ 8 weeks；
3. No abnormality in chest imaging in the past 3 months (or there is abnormality but the investigator judges it not the cause of chronic cough)；
4. FEV1% pred>70%；FEV1/FVC>70%；
5. VAS≥30 in the past 48 hours;
6. Non-smokers or patients smoked less than 10 pack-years;
7. Candidates voluntarily participate in and abide by the relevant regulations of the study, can cooperate with corresponding inspections, follow the follow-up plan, and voluntarily sign written informed consent.

Exclusion Criteria:

1. Patients received inhaled or oral corticosteroids or leukotriene receptor antagonist in previous 4 weeks;
2. Patients with history of upper respiratory tract infection in the past 8 weeks;
3. Patients taking angiotensin-converting enzyme inhibitors in previous 8 weeks;
4. Female subjects who are pregnant, breast-feeding or risk of becoming pregnant during the study;
5. Combined with a definite history of pulmonary diseases such as bronchiectasis, pulmonary interstitial disease, and pulmonary hypertension. Combined with other serious diseases (such as cardiovascular system diseases, metabolic system diseases, immune system diseases, nervous system diseases, etc.) that may affect the normal process of this study;
6. Participating in other drug clinical trial projects.