Characterizing COPD Patients and Controls in the ECLIPSE Study

Power calculation was based on precision of effect estimates in COPD subgroups for rate of decline in FEV₁ over 3 years (confidence interval width of at most 15 mL/year in rate of FEV₁ decline). The sizes of the control groups were based on both the ability to detect a difference of at least 16.5 mL/year rate of decline in FEV₁ between COPD patients and controls, and to detect a 50% increase in exposure (required 5-7 COPD patients per control) for any diagnostic test. Based upon these calculations, we studied 2164 patients with COPD (GOLD stage 2-4), 337 smoking controls and 245 non-smoking controls (Figure 1). Inclusion criteria were as follows [4 (link)]. COPD patients: (1) Male/female subjects aged 40-75 years; (2) Baseline post-bronchodilator FEV₁ < 80% of the reference value and FEV₁/FVC ≤0.7; and, (3) Current or ex-smokers with a smoking history of ≥10 pack-years. Smoker controls: (1) Male/female subjects aged 40-75 years, who are free from significant disease as determined by history, physical examination and screening investigations; (2) Baseline post-bronchodilator FEV₁ > 85% of the reference value and FEV₁/FVC > 0.7; and, (3) Current or ex-smokers with a smoking history ≥10 pack-years. Non smoking controls: (1) Male/female subjects aged 40-75 years, who are free from significant disease as determined by history, physical examination and screening investigations; (2) Baseline post-bronchodilator FEV₁ > 85% of the reference value and FEV₁/FVC > 0.7; and, (3) Smoking history of <1 pack-year. Besides, all participants: (4) signed and dated their written informed consent prior to participation (which had been approved by the Ethics Committees of all participating institutions); and, (5) had to have the ability to comply with the requirements of the protocol and be available for study visits over 3 years. Key exclusion criteria were the presence of a respiratory disorder other than COPD, other significant inflammatory diseases or a reported COPD exacerbation within 4 weeks of enrolment [4 (link)]. COPD patients were recruited from the outpatient clinics of the participating centres (Figure 1). Smoker and non-smoker controls were recruited through site databases and other methods (advertisements in local newspapers and television/radio stations) where appropriate. Figure 2 presents the variability of age (panel A), gender (panel B), smoking status (panel C) and FEV₁ (panel D) in the three groups of individuals recruited into ECLIPSE (COPD patients, smokers and non-smokers with normal lung function) by each of the 46 participating centres.