What Measures of Disease Status Are Useful Indices of Therapeutic Benefit?
Demonstration of airflow limitation (e.g., decreased FEV1) is essential for diagnosis and is the best known predictor of outcome in COPD. Hence, decline in postbronchodilator FEV1 over time has been used as the “gold standard” measure of disease progression in premorbid COPD. However, emerging evidence indicates that alternative measures, such as inspiratory capacity, may better reflect the ventilatory dysfunction in COPD (61, 62). Furthermore, reliance on FEV1 may cause studies to miss beneficial effects of therapies such as increased exercise capacity, quality of life, or cognitive function, or lessened dyspnea, cough, sputum production, depression, or frequency or severity of exacerbations (63). Alternative measures are needed that better reflect the clinical status of patients with COPD and allow detection of clinically important responses to therapies. It is noteworthy that, in a trial of alpha1-antitrypsin augmentation in patients deficient in this protein, progression of emphyse
