David Augustine Lynch MBBCh, Presenter: Research support, Siemens AG Scientific Advisor, PAREXEL International Corporation Consultant, Boehringer Ingelheim GmbH Consultant, InterMune, Inc Consultant, Gilead Sciences, Inc Consultant, F. Hoffmann-La Roche Ltd Consultant, Veracyte, Inc Research support, Johnson & Johnson Research support, AstraZeneca PLC

Douglas C. Everett PhD, Abstract Co-Author: Nothing to Disclose

Eric A. Hoffman PhD, Abstract Co-Author: Founder, VIDA Diagnostics, Inc Shareholder, VIDA Diagnostics, Inc

John D. Newell MD, Abstract Co-Author: Research Consultant, Siemens AG Research Grant, Siemens AG Consultant, WebMD Health Corp Author, Springer Science+Business Media Deutschland GmbH Consultant, VIDA Diagnostics, Inc

Francine Jacobsen MD, Abstract Co-Author: Nothing to Disclose

Barry J. Make, Abstract Co-Author: Nothing to Disclose

To determine in a population of cigarette smokers whether distinct subgroups defined by quantitative CT measures of emphysema and gas trapping differ in symptoms, quality of life, or exacerbation frequency.

We studied 8144 current or former cigarette smokers enrolled in the COPDGene® study. All underwent inspiratory and expiratory volumetric CT with automated quantification of % low attenuation areas (LAA) for estimation of emphysema and gas trapping, using thresholds of -950 on inspiratory CT (LAA-950 insp) and -856 on expiratory CT (LAA-856 exp). Normal cutoff values for these parameters, based on 92 normal subjects, were 5.8% for % LAA-950insp, and 24.3% for % LAA-856exp. Cutoff values were adjusted for current smokers. Dyspnea was evaluated by MMRC questionnaire, respiratory symptoms by St George Respiratory Questionnaire, and quality of life by SF-36 questionnaire. We used binary recursive partitioning (tree function in R) to identify subgroup differences in clinical outcomes.    

Of the 8144 subjects, 768 (9%) met criteria for emphysema without gas trapping (“emphysema”), 579 (7%) had gas trapping without emphysema (“gas trapping”), 2413 (30%) had mixed gas trapping and emphysema, and 4384 (54%) did not meet criteria for emphysema or gas trapping. Compared with the emphysema group, the gas trapping group was significantly older, had shorter 6 minute walk distance, higher frequency of exacerbations, and had higher scores for dyspnea, respiratory symptoms, and physical component of SF-36. When binary recursive partitioning was used, a cutoff value of approximately 40% for gas trapping identified dichotomous subgroups of severity, assessed by FEV1% predicted, FEV1/FVC ratio, MMRC score, 6 minute walk distance, exacerbation frequency, and St George Respiratory questionnaire.

Quantitative CT assessment of emphysema and gas trapping identifies subgroups of subjects with clinically significant differences in disease severity. 

Quantitative CT may be used to identify important clinically important subtypes of COPD.

Lynch, D, Everett, D, Hoffman, E, Newell, J, Jacobsen, F, Make, B, Quantitative CT Can Define Clinically Different Subgroups of Cigarette Smokers.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14015032.html