The challenges of recruiting never-smokers with chronic obstructive pulmonary disease from the large population-based...

A substantial proportion of individuals with COPD have never smoked, and it is implied to be more common than previously anticipated but poorly studied.

To describe the process of recruitment of never-smokers with COPD from a population-based cohort (n = 30 154).

We recruited never-smokers with COPD, aged 50-75 years, from six University Hospitals, based on: 1) post broncho-dilator forced expiratory volume in 1 second/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 due to previous smoking or declined participation. We also applied a lower limit of normal (LLN) of FEV₁/FVC (z-score<-1.64) according to the Global Lung Initiative to ensure a stricter definition of airflow obstruction.

Data on respiratory symptoms, health status, and medical history were collected from 492 individuals, since 32 were excluded at a second data review (declined or previous smoking), prior to the first visit. Due to not matching the required lung function criteria at a second spirometry, an additional 334 (68%) were excluded. These exclusions were by reason of: 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, Oxygen saturation: 97% and BMI: 26.8 kg/m².

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 spirometry assessments for improved accuracy in diagnosing COPD.