Inclusion Criteria:
\- The subject voluntarily participates in this study, complies with the study regulations, understands, agrees to, and cooperates with the required examinations, adheres to the follow-up plan, and voluntarily signs the written informed consent form.
Outpatients, with age between 18 and 70 years old (inclusive).
Newly diagnosed with Cough Variant Asthma (CVA) based on clinical symptoms and pulmonary function results, according to the Chinese Bronchial Asthma Prevention and Treatment Guidelines (2024 Edition) and the Guidelines for the Diagnosis and Treatment of Cough (2021 Edition). This involves chronic cough (lasting over 8 weeks) without accompanying wheezing symptoms or signs, often occurring at night and/or early morning and worsening after exercise. All patients must meet at least one of the following pulmonary function criteria, indicating variable airflow limitation, as objective evidence for asthma diagnosis:
Objective Tests for Variable Airflow Limitation:
1. Positive bronchodilator test: An increase in Forced Expiratory Volume in one second (FEV1) of ≥12% and an absolute increase in FEV1 of ≥200 ml after inhalation of a bronchodilator; OR an increase in FEV1 of ≥12% compared to baseline and an absolute increase of ≥200 ml after 4 weeks of anti-inflammatory treatment containing Inhaled Corticosteroids (ICS) (excluding respiratory infections).
2. Positive bronchial provocation test: Commonly used inhaled agents are methacholine or histamine. A positive result is typically defined as a ≥20% decrease in FEV1 after inhalation of the provoking agent, indicating the presence of airway hyperresponsiveness. Bronchial provocation test can be performed when FEV1 is ≥70% of predicted value (excluding respiratory infections within 4 weeks). If FEV1 is \<70% of predicted value, a bronchodilator test is prioritized.
3. Average daily diurnal variation in Peak Expiratory Flow (PEF) \>10% (calculated as the sum of daily PEF diurnal variation for at least 7 consecutive days divided by the total number of days), excluding respiratory infections.
Cough severity score (CET) \> 5 points. Patients previously diagnosed with CVA who discontinued inhaled medications for more than 3 months for any reason and now meet the above criteria.
Exclusion Criteria:
\- Inability to cooperate with the diagnostic tests for asthma or uncooperative for other reasons.
Pregnancy. Comorbid severe diseases of other systems (e.g., cardiovascular, metabolic, immune, nervous, urinary, hematological) that may interfere with the normal conduct of this study.
A clear history of upper respiratory tract infection within the 4 weeks prior to enrollment.
History of alcohol abuse or substance abuse, or history of psychiatric illness, antagonistic personality, ulterior motives, paranoia, or other emotional or intellectual problems that may compromise the validity of informed consent or participation in the study.
Chest imaging indicates clinically significant abnormalities related to the symptoms.
Smoking: Defined as having smoked more than 100 cigarettes in one's lifetime and having smoked within the past 5 years. Otherwise, considered a non-smoker.
Current use of ACEI (Angiotensin-Converting Enzyme Inhibitor) medications. Concurrent participation in another drug clinical trial, or deemed unsuitable for inclusion in this study by the investigator for other reasons.
