SERETIDE 50/500mcg Versus Tiotropium Bromide On Exacerbation Rates In Severe Chronic Obstructive Pulmonary Disease

Inclusion criteria: * Established clinical history of moderate to severe COPD. * Post bronchodilator FEV1 of \< 50% of predicted normal. * FEV1 / FVC ratio \<70%. * Reversibility to 400mcg albuterol of less or equal to 10 predicted at Visit 1. * Free from exacerbation in the 6 weeks prior to screening. * Current or former smoker with a smoking history of = 10 pack-years and has a history of COPD exacerbations. Exclusion criteria: * Current asthma, eczema, atopic dermatitis and/or allergic rhinitis. * Has a known respiratory disorder other than COPD (e.g. lung cancer, sarcoidosis, tuberculosis or lung fibrosis). * Has narrow-angle glaucoma, prostatic hyperplasia or obstruction of the neck of the bladder that in the opinion of the investigator should prevent the subject from entering the study. * Has undergone lung transplantation and/or lung volume reduction. * Female who is a nursing mother. * Requires regular (daily) long-term oxygen therapy (LTOT). * Is receiving beta-blockers (except eye drops). * Has a serious, uncontrolled disease likely to interfere with the study. * Has received any other investigational drugs within the 4 weeks prior to Visit 1. * Has, in the opinion of the investigator, evidence of alcohol, drug or solvent abuse. * Has a known or suspected hypersensitivity to beta2-agonists, inhaled corticosteroids, anticholinergic agents or any components of the formulations (e.g. lactose or milk protein).