Racial Differences in CT Phenotypes in COPD

Background: Whether African Americans (AA) are more susceptible to COPD than non-Hispanic Whites (NHW) and whether racial differences in disease phenotype exist is controversial. The objective is to determine racial differences in the extent of emphysema and airway remodeling in COPD. Methods: First, 2,500 subjects enrolled in the COPDGene study were used to evaluate racial differences in quantitative CT (QCT) parameters of % emphysema, air trapping and airway wall thickness. Independent variables studied included race, age, gender, education, BMI, pack-years, smoking status, age at smoking initiation, asthma, previous work in dusty job, CT scanner and center of recruitment. Results: Of the 1,063 subjects with GOLD Stage II-IV COPD, 200 self-reported as AA. AAs had a lower mean % emphysema (13.1 % vs. 16.1%, p = 0.005) than NHW and proportionately less emphysema in the lower lung zones. After adjustment for covariates, there was no statistical difference by race in air trapping or airway wall thickness. Measured QCT parameters were more predictive of poor functional status in NHWs compared to AAs. Conclusions: AAs have less emphysema than NHWs but the same degree of airway disease. Additional factors not easily assessed by current QCT techniques may account for the poor functional status in AAs.