Figure 1.

Chronic obstructive pulmonary disease (COPD) results from an interaction between genetic predisposition of some individuals with different causative agents over time. It goes through a period (pre-COPD) where the operational threshold that is used to define airflow limitation has not been reached, but symptoms, structural abnormalities detectable with imaging, or functional dysfunction detectable with lung function testing may identify individuals at higher risk of COPD development. Finally, a full-blown spirometrically detectable phase is reached either at young (<50 yr) or older (⩾50 yr) age. AAT = alpha-1-antitrypsin deficiency; PRISM = preserved ratio impaired spirometry.