title: Emphysema and DLCO predict a clinically important difference for 6MWD decline in COPD.
abstract: BACKGROUND
  Exercise impairment is a central feature of chronic obstructive pulmonary disease (COPD), and a minimal clinically important difference (MCID) for 6-min walk distance (6MWD) decline (>30 m) has been associated with increased mortality. The predictors of the MCID are not fully known. We hypothesize that physiological factors and radiographic measures predict the MCID.
  
  
  METHODS
  We assessed 121 COPD subjects during 2 years using clinical variables, computed tomographic (CT) measures of emphysema, and functional measures including diffusion lung capacity for carbon monoxide (DLCO). The association between an MCID for 6MWD and clinical, CT, and physiologic predictors was assessed using logistic analysis. The C-statistic was used to assess the predictive ability of the models.
  
  
  RESULTS
  Forty seven (39%) subjects had an MCID. In an imaging-based model, log emphysema and age were the best predictors of MCID (emphysema Odds Ratio [OR] 2.47 95%CI [1.28-4.76]). In a physiologic model, DLCO, age, and male gender were selected the best predictors (DLCO OR 1.19 [1.08-1.31]). The C-statistic for the ability of these models to predict an MCID was 0.71 and 0.75, respectively.
  
  
  CONCLUSIONS
  In COPD patients the burden of emphysema on CT scan and DLCO predict a clinically meaningful decline in exercise capacity.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
authors.forename: Alejandro A
authors.initials: AA
authors.lastname: Díaz
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
authors.forename: Victor
authors.initials: V
authors.lastname: Pinto-Plata
authors.affiliation: Department of Pulmonary Diseases, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile.
authors.forename: Camila
authors.initials: C
authors.lastname: Hernández
authors.affiliation: Department of Pulmonary Diseases, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile.
authors.forename: Javier
authors.initials: J
authors.lastname: Peña
authors.affiliation: Department of Radiology, Hospital Clínico José Joaquín Aguirre, Universidad de Chile, Santiago, Chile.
authors.forename: Cristóbal
authors.initials: C
authors.lastname: Ramos
authors.affiliation: Department of Radiology, Hospital Clínico José Joaquín Aguirre, Universidad de Chile, Santiago, Chile.
authors.forename: Juan C
authors.initials: JC
authors.lastname: Díaz
authors.affiliation: Department of Diabetes, Nutrition and Metabolism, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile.
authors.forename: Julieta
authors.initials: J
authors.lastname: Klaassen
authors.affiliation: Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.
authors.forename: Cecilia M
authors.initials: CM
authors.lastname: Patino
authors.affiliation: Department of Pulmonary Diseases, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile.
authors.forename: Fernando
authors.initials: F
authors.lastname: Saldías
authors.affiliation: Department of Pulmonary Diseases, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile. Electronic address: odiazp@vtr.net.
authors.forename: Orlando
authors.initials: O
authors.lastname: Díaz
mesh_terms: D000368:Aged; D002248:Carbon Monoxide / Q000378:metabolism*; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D011653:Pulmonary Diffusing Capacity / Q000379:methods*; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications / Q000378:metabolism / Q000503:physiopathology*; D011656:Pulmonary Emphysema / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology; D014057:Tomography, X-Ray Computed; D016138:Walking
chemical_list: D002248:Carbon Monoxide
keywords: %LAA; COPD; CT; Emphysema; Six-minute walk distance