Bronchodilator (BD) reversibility: at least 12% reversibility and 200ml improvement in post-BD FEV1 after administration of salbuterol/albuterol or levalbuterol/levosalbutamol at the screening visit. Alternatively, subjects are eligible if there is a documented history of at least 12% reversibility and 200ml improvement in the last 12 months together with any of the following criteria