We recommend:
• Studies that determine which index or indices best stratify patients for the purpose of determining disease severity or recommending treatment.
• Studies that determine if short-term changes in these indices or other measures (e.g. lung function, CT findings and biomarkers) are useful surrogate markers of medium- or long-term patient-centred outcomes, thus shortening the time needed to complete therapeutic trials.
• Studies that contribute to a better understanding of the pathogenesis, impact, prevention and treatment of concomitant diseases in patients with COPD.