- Severity of Disease: Subjects must demonstrate at Screening: <a post-bronchodilator FEV1 <50% predicted normal OR a post-bronchodilator FEV1 <80% predicted normal and a documented history of >=2 moderate exacerbations or one severe (hospitalized) exacerbation in the previous 12 months. Subjects must also have a measured post albuterol/salbutamol FEV1/FVC ratio of <0.70 at screening. Note: Percent predicted will be calculated using the European Respiratory Society Global Lung Function Initiative reference equations. Note: A documented history of a COPD exacerbation (e.g., medical record verification) is a medical record of worsening COPD symptoms that required systemic/oral corticosteroids and/or antibiotics (for a moderate exacerbation) or hospitalization (for a severe exacerbation). Prior use of antibiotics alone does not qualify as an exacerbation history unless the use was associated with treatment of worsening symptoms of COPD, such as increased dyspnoea, sputum volume, or sputum purulence (colour). Subject verbal reports are not acceptable.