Determining the optimal approach to identifying individuals with chronic obstructive pulmonary disease

INTERVENTION: 1. Participants will undertake lung function tests (i.e. peak flow measurement, microspirometry and post‐bronchodilator spirometry), a wheeze‐detecting device (i.e. wheezometer) and a case‐finding questionnaire 2. Further questionnaires will be completed during the study; a screening questionnaire and a follow‐up questionnaire. All participants receive the case‐finding tests, with half randomised to receive the tests straight away and the remainder will receive the tests approximately 6 months later. CONDITION: Chronic obstructive pulmonary disease (COPD) ; Respiratory ; Chronic obstructive pulmonary disease (COPD) PRIMARY OUTCOME: Effectiveness of diagnostic pathways ‐ aim to identify the most effective pathway for use as the routine service model in primary care SECONDARY OUTCOME: 1. Cost‐effectiveness of COPD case‐finding pathway; 2. Efficiency of COPD case‐finding pathway; 3. Impact on smoking behaviour INCLUSION CRITERIA: Current smokers aged 35 years or more who are registered with participating GP practices