a. with known other chronic respiratory diseases except COPD (such as asthma, tuberculosis, bronchiectasis, interstitial lung disease, occupational lung diseases, sarcoidosis, lung cancer, et al); b. had been accepted lung lobectomy or transplantation; c. be ill with severe, or uncontrolled systemic diseases other than COPD (such as psychiatry diseases, chronic liver diseases, heart failure, auto-immunity diseases, chronic renal diseases, et al ); d. Alcoholism, drug or solvents addition; e. Acute respiratory infection in 4 weeks (rhinitis, pharyngitis, acute tracheobronchitis, pneumonia, etc.)