Prevalence of chronic obstructive pulmonary disease (COPD) defined by different criteria by region. The dark grey bar represents ‘symptom-based COPD’, grey bar represents ‘doctor-diagnosed COPD’ and the white bar represents ‘symptom-based or doctor-diagnose... Prevalence of chronic obstructive pulmonary disease (COPD) defined by different criteria by region. The dark grey bar represents ‘symptom-based COPD’, grey bar represents ‘doctor-diagnosed COPD’ and the white bar represents ‘symptom-based or doctor-diagnosed COPD’ participants. Om P Kurmi et al. BMJ Open Resp Res 2018;5:e000267 ©2018 by British Thoracic Society