In addition to the analyses of the entire COPDGene population listed above, separate analyses of the GOLD Stage 1 cases will be performed. We will attempt to identify a normal subgroup and an early disease subgroup within this phenotypic category based on their CT emphysema, CT airway, and spirometric characteristics. The relationship of this “normal” subset to functional impairment and disease impact measures will be assessed. We hypothesize that individuals in the putative normal subgroup will have less functional impairment, less evidence for disease impact, and fewer exacerbations. Ultimately, longitudinal follow-up will be required to determine if the hypothesized “normal” subgroup of GOLD 1 subjects are less likely to progress to full airflow obstruction. However, cross-sectional analysis of GOLD 1 subjects will determine whether clinical heterogeneity can be discerned within these groups using CT data.
