Phenotypic characterisation of early COPD: a prospective case-control study.

The phenotypic characteristics of chronic obstructive pulmonary disease (COPD) in individuals younger than 50 years of age (early COPD) are not well defined. This prospective, multicentre, case-control study sought to describe these characteristics and compare them with those of smokers (≥10 pack-years) of similar age with normal spirometry (controls). We studied 92 cases (post-bronchodilator forced expiratory volume in 1 s (FEV)/forced vital capacity (FVC) <0.