Clinical Research Directory

Inclusion Criteria: * Able and willing to provide written informed consent and complete study assessments and follow-up. * Pre-COPD participants: age 35 years or older, without spirometric airflow obstruction, and with COPD risk factors and/or early clinical, pulmonary function, or imaging features according to the study protocol. * Stable COPD participants: age 40 years or older, with a diagnosis of COPD based on post-bronchodilator FEV1/FVC \< 0.70, in stable condition without acute exacerbation within the specified period before enrollment, and classified as GOLD stage 1-2 or GOLD stage 3-4. * Acute exacerbation of COPD participants: age 40 years or older, with COPD based on post-bronchodilator FEV1/FVC \< 0.70 and an acute exacerbation meeting protocol-defined criteria, enrolled within the protocol-defined time window. * Healthy control participants: age 35 years or older, without COPD based on symptoms, pulmonary function, and chest imaging criteria defined in the protocol. * Participants in COPD-related groups must have traditional Chinese medicine syndrome assessment information available according to the study protocol. Exclusion Criteria: * Unable or unwilling to provide informed consent or comply with study procedures and follow-up. * Respiratory diseases or other conditions that may substantially interfere with COPD-related assessments, including protocol-defined asthma, severe bronchiectasis, active pulmonary tuberculosis, lung cancer, interstitial lung disease, or other major pulmonary diseases. * Severe cardiovascular, hepatic, renal, hematologic, neurologic, psychiatric, malignant, immune, or infectious diseases that, in the investigator's judgment, make participation inappropriate or may affect study assessments. * Recent systemic glucocorticoid or antibiotic use, or other protocol-defined medication exposures, that may affect study-related sample collection or assessment. * Pregnancy or lactation, where applicable according to participant group. * Participation in another clinical study that may interfere with this study. * Any other condition judged by the investigator to make the participant unsuitable for this study.