Recruiting never-smokers with COPD from the population-based Swedish Cardiopulmonary bioimage study (SCAPIS)

<bold>Background:</bold> A substantial proportion of individuals with COPD have never smoked. <bold>Aim:</bold> To describe the process of recruitment of never-smokers with COPD from a population-based study (n=30 154). <bold>Methods:</bold> We recruited never-smokers with COPD, aged 50-75, from six University Hospitals, based on: 1) postbroncho-dilator forced expiratory volume in 1 sec /forced vital capacity (FEV₁/FVC)< 0.70 and 2) FEV₁ 50-100% of predicted value and 3) being never-smokers (self-reported). In total 862 SCAPIS participants were identified of which 652 were reachable and agreed to a first screening by telephone. Altogether 128 (20%) were excluded (declined, have smoked). We also applied lower limit of normal (LLN) of FEV₁/FVC (z-score<-1.64) according to Global Lung Initiative to ensure only participants with airflow obstruction were included. <bold>Results:</bold> Data on respiratory symptoms, health status and medical history were collected from 492 individuals, since 32 were excluded at a second data review (declined, have smoked), prior to the first visit. Due to not matching lung function criteria at a second spirometry, an additional 334 (68%) were excluded. The mismatches were FEV₁/FVC ≥ 0.7 (49%), FEV₁>100% of predicted (26%) or z-score ≥ -1,64 (24%). Finally, 154 never-smokers with COPD were included: 56 (36%) women, (mean) age 60 years, FEV₁ 84% of predicted, FEV₁/FVC: 0.6, z-score: -2.2, O₂ saturation: 97% and BMI: 26.8 kg/m². <bold>Conclusion:</bold> The challenges of a recruitment process of never-smokers with COPD were shown including the importance of correct spirometry testing and strict inclusion criteria. Our findings highlight the importance of repeated assessments for improved accuracy in diagnosing COPD.