Table 1. Comparative studies.

Study	Study design and setting	Eligibility criteria	Intervention	Comparator	COPD definition	COPDa/eligibleb	Limitations
Bunker 200922	RCT: nurse-led case finding using spirometry versus usual care in four practices (recruitment dates not reported).	Inclusion criteria: ever smokers aged 40–80 years. Exclusion criteria: known diagnosis of COPD, cognitive impairment, non-English speaking and <2 visits to practice in the preceding year.	Case finding arm: spirometry (unclear whether pre- or post-BD) performed by practice nurses.	Routine care.	FEV1/FVC<70% (unclear whether pre- or post-BD).	Case finding: 10/400 (2.5%) Routine care: 1/408 (0.2%). Difference in yield=2.3% (95% CI 0.7 to 3.9%).	Method of randomisation was not described. Inadequate outcome ascertainment. Outcome assessors were not blinded. Unclear whether intervention groups were comparable.
Dirven 201323	Cluster RCT: patient versus practice-managed scoring of a screening questionnaire in 16 general practices from May to September 2012.	Inclusion criteria: age 40–70 years. Exclusion criteria: previous diagnosis of asthma, COPD or significant lung disease. Patients using oxygen supplementation and those with impaired mobility were also excluded.	Patient-managed arm Stage 1: patients were mailed the Respiratory Health Screening Questionnaire, self-calculated risk of COPD and advised to consult GP if score was >19.5. Stage 2: post-BD spirometry for subjects scoring >19.5.	Practice-managed arm Stage 1: patients were mailed the questionnaire, but scoring was performed by healthcare staff. Stage 2: post-BD spirometry on subjects scoring >19.5.	Post-BD FEV1/FVC<0.7 and physician’s clinical evaluation.	Patient managed: 25/6393 (0.4%). Practice managed: 48/3715 (1.3%). Difference in yield=0.9% (95% CI 0.5 to 1.3%).	Unclear whether intervention groups were comparable (although practices were stratified by socioeconomic status). Unclear whether outcome assessors were blinded.
Haroon 201316	RCT: active versus opportunistic case finding in two general practices from May 2010 to January 2011.	Inclusion criteria: ever smokers aged 35–79 years. Exclusion criteria: prior diagnosis of COPD or asthma.	Active arm Stage 1: postal screening questionnaire. Stage 2: pre-BD spirometry in subjects with symptoms.	Opportunistic arm Stage 1: opportunistic screening questionnaire provided at routine primary care visits. Stage 2: pre-BD spirometry in subjects with symptoms.	Pre-BD FEV1/FVC<0.7 with FEV1<80% predicted, lack of reversibility (reversibility defined as increase in FEV1 of 200 ml and 15% from pre-BD FEV1) and presence of respiratory symptoms.	Active: 10/815 (1.2%). Opportunistic: 6/819 (0.7%). Difference in yield=0.5% (95% CI −0.5 to 1.5%).	Unclear whether outcome assessors were blinded. Poor spirometry attendance.
Konstantikaki 201125	Non-randomised controlled trial: open spirometry programme versus case finding strategy in 24 semirural general practices from November 2008 to October 2009.	Inclusion criteria: >30 years. Exclusion criteria: history of respiratory tract infection in previous 4 weeks and inability to perform spirometry.	Open spirometry arm: public invitation through local advertisements offering free spirometry to people with chronic respiratory symptoms.	Case finding strategy: primary care physicians identified patients with a probable diagnosis of COPD in their daily practice and spirometry performed by research team.	History of exposure to noxious particles or gases, particularly smoking, compatible symptoms and post-BD FEV1/FVC<0.7.	Open spirometry: 76/1084 (7.0%). Case finding: 56/219 (25.6%). Difference in yield=18.6% (95% CI 12.6 to 24.6%).	No randomisation. Poor description of recruitment, selection criteria and spirometry.

Abbreviations: BD, bronchodilator; CI, confidence interval; COPD, chronic obstructive pulmonary disease; FEV₁, forced expiratory volume in 1 s; FVC, forced vital capacity; RCT, randomised controlled trial.

^aSubjects newly diagnosed with COPD.

^bEligible subjects.