STUDY OUTLINE: Chronic obstructive pulmonary disease (COPD) is defined as airflow limitation on spirometry with an FEV1/FVC ratio less than 0.7 or less than the lower limit of normal. However, patients with preserved lung function may still experience respiratory symptoms, exacerbations, and accelerated decline in lung function similar to COPD. It is also understandable that there are racial differences in COPD outcomes and COPD underdiagnosis rates. Thus, there are knowledge gaps in understanding the prevalence of emphysema on CT in persons with normal lung function and whether there is a difference in the prevalence of emphysema in black and white adults.
Overall, the study found that emphysema often occurs before spirometry results become abnormal. In addition, black men have a higher prevalence of emphysema than white men. This study was limited by the inability to examine CT imaging and spirometry simultaneously. Imaging was obtained five years before spirometry, emphysema is a progressive and irreversible disease, so this may lead to an overall underestimation of the prevalence of emphysema. However, the results of these studies are important because they suggest that emphysema can precede the detection of abnormal spirometry results and that the incidence of these emphysema may be influenced by ethnicity.
The CARDIA (Coronary Artery Risk Development in Young Adults) study was a multicenter, population-based longitudinal cohort study that enrolled 5,115 black and white participants aged 18 to 30. Spirometry and clinical data were acquired from 2015 to 2016, and CT scans were acquired from 2010 to 2011. The primary outcome measure was the prevalence of emphysema among participants, with various measures of normal spirometry results, including FEV1/FVC ratio greater than or equal to 0.7 or greater than or equal to the lower limit of normal, stratified by sex and self-reported ethnicity .
Outcomes from the primary analysis were assessed by sex-specific multivariate logistic regression to calculate adjusted emphysema prevalence and age, smoking status, and pack-years. In patients with emphysema, ethnicity-specific predicted values for FEV1 ranged from 80% to 99% despite normal spirometry results, according to a preliminary analysis. The prevalence of emphysema was 3.9 times higher in black men than in white men (95% confidence interval [CI], 2.1 to 7.1 times), and 1.9 times higher in black women than in white women (95% CI, 1.0 to 3.8 times). Among patients with FEV1 between 100% and 120% of predicted, the prevalence was 6.4-fold higher in black men than in white men (95% CI, 2.2- to 18.7-fold). The prevalence of emphysema was similar in black and white women (2.6% and 2.0%). Overall, this study shows that emphysema is present even with normal spirometry results, and that the prevalence of emphysema is higher in black men than in white men.