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Prevalence and grade of (A) airflow obstruction and (B) emphysema by chronic obstructive pulmonary disease (COPD) group. COPD groups: “no COPD” (FEV1:FVC ≥70%); “undiagnosed COPD” (FEV1:FVC <70% and no reported history of COPD); and “known COPD” (FEV1:FVC <70% and a reported history of COPD). FEV1 = forced expiratory volume in 1 second; FVC = forced vital capacity; GOLD = Global Initiative for Obstructive Lung Diseases.
