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Longitudinal Change in the BODE Index Predicts Mortality in Severe Emphysema

¹ Division of Pulmonary and Critical Care Medicine, University of Michigan Medical Center, Ann Arbor, Michigan; ² Department of Biostatistics and Medical Informatics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin; ³ Division of Pulmonary and Critical Care Medicine, Johns Hopkins University, Baltimore, Maryland; ⁴ Department of Biostatistics, University of Michigan School of Public Health, Ann Arbor, Michigan; ⁵ Pulmonary Section, Ann Arbor Veterans Affairs Medical Center, Ann Arbor, Michigan; ⁶ Pulmonary and Critical Care Medicine, Temple University, Philadelphia, Pennsylvania; ⁷ Division of Pulmonary Medicine, Brigham and Women's Hospital, Boston, Massachusetts; ⁸ Division of Pulmonary and Critical Care Medicine, National Jewish Medical and Research Center, Denver, Colorado; ⁹ Department of Medicine, University of California, San Diego, San Diego, California; ¹⁰ Division of Pulmonary and Critical Care Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania; ¹¹ Division of Lung Diseases, National Heart, Lung, and Blood Institute, Bethesda, Maryland; ¹² Division of Pulmonary Medicine, Cedars Sinai Medical Center, Los Angeles, California; ¹³ Section of Thoracic Surgery, Beth Israel Deaconess Medical Center, Boston, Massachusetts; ¹⁴ Department of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania; and ¹⁵ Pulmonary, Critical Care, and Sleep Medicine Division, St. Elizabeth's Medical Center, Boston, Massachusetts

Correspondence and requests for reprints should be addressed to Fernando J. Martinez, M.D., M.S., 1500 E. Medical Center Drive, 3916 Taubman Center, University of Michigan Health System, Ann Arbor, MI 48109-0360. E-mail: fmartine{at}umich.edu

Rationale: The predictive value of longitudinal change in BODE (Body mass index, airflow Obstruction, Dyspnea, and Exercise capacity) index has received limited attention. We hypothesized that decrease in a modified BODE (mBODE) would predict survival in National Emphysema Treatment Trial (NETT) patients.

Objectives: To determine how the mBODE score changes in patients with lung volume reduction surgery versus medical therapy and correlations with survival.

Methods: Clinical data were recorded using standardized instruments. The mBODE was calculated and patient-specific mBODE trajectories during 6, 12, and 24 months of follow-up were estimated using separate regressions for each patient. Patients were classified as having decreasing, stable, increasing, or missing mBODE based on their absolute change from baseline. The predictive ability of mBODE change on survival was assessed using multivariate Cox regression models. The index of concordance was used to directly compare the predictive ability of mBODE and its separate components.

Measurements and Main Results: The entire cohort (610 treated medically and 608 treated surgically) was characterized by severe airflow obstruction, moderate breathlessness, and increased mBODE at baseline. A wide distribution of change in mBODE was seen at follow-up. An increase in mBODE of more than 1 point was associated with increased mortality in surgically and medically treated patients. Surgically treated patients were less likely to experience death or an increase greater than 1 in mBODE. Indices of concordance showed that mBODE change predicted survival better than its separate components.

Conclusions: The mBODE demonstrates short- and intermediate-term responsiveness to intervention in severe chronic obstructive pulmonary disease. Increase in mBODE of more than 1 point from baseline to 6, 12, and 24 months of follow-up was predictive of subsequent mortality. Change in mBODE may prove a good surrogate measure of survival in therapeutic trials in severe chronic obstructive pulmonary disease.

Clinical trial registered with www.clinicaltrials.gov (NCT 00000606).

Key Words: chronic obstructive pulmonary disease • survival • multidimensional index

AT A GLANCE COMMENTARY Scientific Knowledge on the Subject The BODE index has prognostic value with respect to chronic obstructive pulmonary disease mortality, although the importance of change in BODE has received limited attention. What This Study Adds to the Field In a cohort of patients with severe emphysema, an increase in modified BODE of more than 1 is associated with increased mortality. Change in modified BODE also predicted survival better than its separate components.