Abstract
Background: Exercise tolerance in COPD is only moderately well predicted by airflow obstruction assessed by FEV1. We determined whether other phenotypic characteristics, including CT scan measures, are independent predictors of 6-min walk distance (6MWD) in the COPDGene cohort. Methods: COPDGene recruits non-Hispanic Caucasian and African American current and ex-smokers. Phenotyping measures include postbronchodilator FEV1 % predicted and inspiratory and expiratory CT lung scans. We defined % emphysema as the percentage of lung voxels, < -950 Hounsfield units on the inspiratory scan and % gas trapping as the percentage of lung voxels, < -856 Hounsfield units on the expiratory scan. Results: Data of the first 2,500 participants of the COPDGene cohort were analyzed. Participant age was 61 ± 9 years; 51% were men; 76% were non-Hispanic Caucasians, and 24% were African Americans. Fifty-six percent had spirometrically defined COPD, with 9.3%, 23.4%, 15.0%, and 8.3% in GOLD (Global Initiative for Chronic Obstructive Lung Disease) stages I to IV, respectively. Higher % emphysema and % gas trapping predicted lower 6MWD (P <.001). However, in a given spirometric group, after adjustment for age, sex, race, and BMI, neither % emphysema nor % gas trapping, or their interactions with FEV 1% predicted, remained a significant 6MWD predictor. In a given spirometric group, only 16% to 27% of the variance in 6MWD could be explained by age, male sex, Caucasian race, and lower BMI as significant predictors of higher 6MWD. Conclusions: In this large cohort of smokers in a given spirometric stage, phenotypic characteristics were only modestly predictive of 6MWD. CT scan measures of emphysema and gas trapping were not predictive of 6MWD after adjustment for other phenotypic characteristics.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 867-875 |
| Number of pages | 9 |
| Journal | CHEST |
| Volume | 141 |
| Issue number | 4 |
| DOIs | |
| State | Published - Apr 2012 |
Bibliographical note
Funding Information:Financial/nonfinancial disclosures: The authors have reported to CHEST the following conflicts of interest: Dr Porszasz is a consultant with Forest Laboratories, Inc; Novartis Pharmaceuticals Corporation; and Boehringer Ingelheim GmbH. Dr Make has received grant funds (controlled by National Jewish Health) from and participated in advisory boards or has been a speaker for the National Heart, Lung, and Blood Institute; Abbott Laboratories; AstraZeneca; Dey Pharma, LP; Forest Laboratories, Inc; MedImmune, LLC; Merck and Company; Novartis Pharmaceuticals Corporation; NycoMed International Management GmbH; Respironics-Philips Healthcare; GlaxoSmithKline plc; Nabi Biopharmaceuticals; Boehringer Ingelheim GmbH; Pfizer Inc; and Synovian Inc. Dr Casaburi has received grant funds (controlled by Los Angeles Biomedical Research Institute) from and participated in advisory boards or has been a speaker for the National Heart, Lung, and Blood Institute; AstraZeneca; Forest Laboratories, Inc; Novartis Pharmaceuticals Corporation; Respironics-Philips Healthcare; Boehringer Ingelheim GmbH; Pfizer Inc; Breath Technologies, Inc; Theratechnologies Inc; F. Hoffman-La Roche Ltd; Osiris Therapeutics Inc; Actelion Pharmaceuticals Ltd; and Bayer Healthcare Pharmaceuticals. Drs Rambod and Crapo have reported that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.
Funding Information:
Funding/Support: The project described was supported by the National Heart, Lung, and Blood Institute [U01HL089897 and U01HL089856] .