Osteoprotegerin (OPG) in Induced Chronic Obstructive Pulmonary Disease (COPD) Sputum

Inclusion Criteria: * Healthy non-smokers * Age \<35 years (younger group) * Aged matched to COPD patients (older group) * Normal spirometry * Subjects are able to give informed consent * Healthy smokers * Age \<35 years (younger group) * Aged matched to COPD patients (older group) * Normal spirometry * Subjects are able to give informed consent Stable COPD patients: Stage I-IV according to the GOLD guidelines (3), (9) * Current and/or ex-smokers with no less than 10 pack-year smoking history * The subjects are able to give informed consent COPD patients with acute exacerbation: Stage I-IV according to the GOLD guidelines (3), (9) * Exacerbation of COPD defined as "an event in the natural course of the disease characterised by a change in the patient's baseline dyspnoea, cough and/or sputum beyond day to day variability sufficient to warrant a change in management" (9) * Current and/or ex-smokers with no less than 10 pack-year smoking history * The subjects are able to give informed consent Asthma patients * Patients diagnosed with asthma * The subjects are able to give informed consent Bronchiectasis patients * Patients with CT-confirmed bronchiectasis * The subjects are able to give informed consent Cystic fibrosis patients * Patients diagnosed with cystic fibrosis * The subjects are able to give informed consent Exclusion Criteria: * Healthy non-smokers and smokers * Upper respiratory infection within the last 4 weeks. * Subjects who have received research medication within the previous one month. * Subjects unable to give informed consent. * Any psychiatric condition rendering the patient unable to understand the nature, scope and possible consequences of the study Stable COPD patients * Patients who have had an exacerbation which required treatment with oral steroids during the last 2 months prior to the visit * Upper respiratory infection within the last 4 weeks * Subjects who have received research medication within the previous one month * Subjects unable to give informed consent * Any psychiatric condition rendering the patient unable to understand the nature, scope and possible consequences of the study COPD patients with acute exacerbation * Subjects who have received research medication within the previous one month * Subjects unable to give informed consent * Any psychiatric condition rendering the patient unable to understand the nature, scope and possible consequences of the study Asthma * Upper respiratory infection within the last 4 weeks * Subjects who have received research medication within the previous one month * Subjects unable to give informed consent. * Any psychiatric condition rendering the patient unable to understand the nature, scope and possible consequences of the study. * Bronchiectasis and cystic fibrosis * Subjects who have received research medication within the previous one month. * Subjects unable to give informed consent. * Any psychiatric condition rendering the patient unable to understand the nature, scope and possible consequences of the study.