Alejandro A Díaz1, Victor Pinto-Plata1, Camila Hernández2, Javier Peña2, Cristóbal Ramos3, Juan C Díaz3, Julieta Klaassen4, Cecilia M Patino5, Fernando Saldías2, Orlando Díaz6. 1. Division of Pulmonary and Critical Care Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA. 2. Department of Pulmonary Diseases, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile. 3. Department of Radiology, Hospital Clínico José Joaquín Aguirre, Universidad de Chile, Santiago, Chile. 4. Department of Diabetes, Nutrition and Metabolism, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile. 5. Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA. 6. Department of Pulmonary Diseases, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile. Electronic address: odiazp@vtr.net.
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. CONCLUSION: In COPD patients the burden of emphysema on CT scan and DLCO predict a clinically meaningful decline in exercise capacity.
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. CONCLUSION: In COPDpatients the burden of emphysema on CT scan and DLCO predict a clinically meaningful decline in exercise capacity.
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