Establish FeNO Cut-off Value for Predicting Budesonide-formoterol Response in Chronic Cough Suggestive of CVA Patients.

This is a multicenter, prospective, single-arm, interventional clinical study to predict the response to budesonide-formoterol treatment in patients with chronic dry or nocturnal cough by determining a cut off value of FeNO. In this study, the response to ICS/LABA treatment is defined as reduction in cough VAS score from baseline of ≥30 mm after 8 weeks of ICS/LABA treatment. Subjects will be treated with Symbicort® 160/4.5 mcg, 1 puff, BID for 8 weeks with 4 study visits: Visit 1 (Day 0), Visit 2 (week 4) and Visit 3, end of study (week 8) and Visit 4, 4 weeks after treatment discontinuation, (week 12). Baseline data will be collected at Day-5 to Day0. This study will be conducted at around 40 study sites in China. Approximately 1000 patients (age ≥18 years old) with dry cough or nocturnal cough symptoms for at least 8 weeks and no other obvious cause for their cough will be enrolled into this study. Disclosure Statement: This is an Interventional study with single arm. Number of Participants: Approximately 1150 participants will be screened to achieve 1000, based on assuming a screen failure rate of approximately 15%. assigned to study intervention. Study Arms and Duration: Single-arm, 2 months Data Monitoring / Other Committee: Not applicable Statistical Methods： In general, descriptive statistics will be provided for the data collected. For continuous variables, mean, standard deviation, median, quartiles, minimum and maximum will be provided, and for categorical variables, frequency counts and percentages for each category will be provided. Missing data will not be imputed unless otherwise specified. The diagnostic value of FeNO to Budesonide-formoterol response will be measured as the area under the curve (AUC) of the receiver-operating characteristic derived from the Logistic regression model. The study is mainly to investigate if FeNO alone can help to distinguish patients with Budesonide-formoterol response or not, and therefore baseline FeNO value will be the only independent variable included in the model. The optimal cutoff value will be selected by consulting clinical experts, and based on comprehensive assessment of AUC, sensitivity, specificity, PPV, and NPV of different FeNO cut points. To perform discovery and validation within the same study, the total sample will be split randomly into discovery and validation datasets by 70% and 30% respectively. For the validation, similar parameters of diagnostic values will be calculated and compared with those based on the discovery dataset.