Association between Emphysema and Chronic Obstructive Pulmonary Disease Outcomes in the COPDGene and SPIROMICS Cohorts: A Post Hoc Analysis of Two Clinical Trials

The use of thoracic computed tomographic (CT) imaging in current and former smokers is becoming increasingly more common because of its widespread availability and utility in lung cancer screening.Prior studies have demonstrated associations between CT measures of emphysema and respiratory symptoms, exacerbations, and mortality (1-5).However, thus far, practical guidance on how to incorporate increasingly available quantitative imaging data into clinical practice is lacking.In this analysis, we use data from two large NIH-sponsored cohort studies, SPIROMICS (Subpopulations and Intermediate Outcomes in COPD Study) and COPDGene (COPD Genetic Epidemiology), to examine the relationship between a readily available metric, CT-based emphysema, and risk for important patient outcomes including symptoms, exacerbations, and mortality.The goal of our analysis is not to advocate for routine CT imaging in chronic obstructive pulmonary disease (COPD) but, rather, to provide clinicians with guidance on how to translate increasingly available quantitative imaging data into information that can guide patient decision-making.We used data from COPDGene and SPIROMICS, both NIH-funded multicenter cohort studies of smokers with and without airflow obstruction.All subjects were age 40-80 years with 10 pack-years or more of exposure (6, 7).Exacerbations were defined by use of an antibiotic and/or steroid, emergency room visit, or hospital admission for a respiratory "flare-up" on the American Thoracic Society Respiratory Disease questionnaire.Exacerbation data for both cohorts were captured via longitudinal follow-up protocols.For both studies, all participants underwent spirometry before and after the administration of a short-acting bronchodilator; postbronchodilator values were used in this