In this study, Estimates based on the presence of airflow limitation are most accurate, since symptoms and self-report clinician diagnosis lack sensitivity and specificity. FEV1 /FVC < 0.7, in combi-nation with a FEV1 < 60% of predicted value, in an individual with cough, sputum production or dyspnea and exposure to risk factors confirms the diagnosis. Cases of COPD could be under diagnosed in the presence of a other severe disease such as coronary artery disease. In the present study, COPD was defined when the FEV1/FVC was <0.7. Absolute FEV1 in litres has been used by other studies but FEV1 in percentage of predicted value is a more reliable parameter because it is adjusted to patient’s age and size.