Current issues of ACP Journal Club are published in Annals of Internal Medicine


Clinical Prediction Guide

The BODE index predicted death in chronic obstructive pulmonary disease

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ACP J Club. 2004 Sep-Oct;141:53. doi:10.7326/ACPJC-2004-141-2-053


Clinical Impact Ratings

GIM/FP/GP: 6 stars

Hospitalists: 7 stars

Pulmonology: 6 stars


Source Citation

Celli BR, Cote CG, Marin JM, et al. The body-mass index, airflow obstruction, dyspnea, and exercise capacity index in chronic obstructive pulmonary disease. N Engl J Med. 2004;350:1005-12. [PubMed ID: 14999112]


Abstract

Question

In patients with chronic obstructive pulmonary disease (COPD), how well does an index comprising the risk factors that reflect the respiratory, perceptive, and systemic aspects of the disease predict outcome?

Methods

Design: 2 cohort studies, 1 for development and 1 for validation.

Setting: Clinics in the United States, Venezuela, and Spain.

Patients: 832 patients (mean age 66 y) who had COPD with a wide range of severity, were in clinically stable condition, and were receiving appropriate therapy. Exclusion criteria were probability of death within 3 years from a cause other than COPD, asthma, inability to take the lung-function and 6-minute walk tests, myocardial infarction within the previous 4 months, unstable angina, or congestive heart failure. 207 patients were recruited from 1995 to 1997 and formed the development cohort; 625 patients were recruited from 1997 to 2003 and formed the validation cohort.

Description of prediction guide: The following variables were assessed for each patient in the development cohort: age, sex, pack-years of smoking, FVC, FEV1, the best of two 6-minute walk tests done 30 minutes apart, degree of dyspnea, body mass index (BMI), functional residual and inspiratory capacities, hematocrit and albumin levels, and degree of comorbid conditions. A logistic regression analysis determined the variables with the strongest association with 1-year mortality. 4 such variables (BMI [B], FEV1 as a percentage of the predicted value as an indication of airflow obstruction [O], score on the modified Medical Research Council [MMRC] dyspnea scale [D], and the distance walked in 6 minutes as an indication of exercise capacity [E]) were included in the BODE index (0 to 10 points). Patients in the validation cohort were seen every 3 to 6 months for ≥ 2 years or until death.

Outcomes: Death from any cause and death from respiratory causes.

Main results

Higher BODE scores were associated with greater risk for death (Table). In a model containing FEV1 or the BODE score as the independent variable, the c statistic for the ability to predict risk for death was greater for the BODE index than for FEV1 (0.74 vs 0.65).

Conclusion

In patients with chronic obstructive pulmonary disease, an index comprising measures of body mass index, degree of airflow obstruction and dyspnea, and exercise capacity predicted all-cause mortality and death from respiratory causes.

Source of funding: No external funding.

For correspondence: Dr. B.R. Celli, St. Elizabeth's Medical Center, Tufts University School of Medicine, Boston, MA, USA. E-mail bcelli@copdnet.org.


Table. BODE index for predicting death in chronic obstructive pulmonary disease*

Outcomes Hazard ratio (95% CI)† P value
Death from all causes 1.34 (1.26 to 1.42) < 0.001
Death from respiratory causes 1.62 (1.48 to 1.77) < 0.001

*BODE = body mass index, airflow obstruction, dyspnea, and exercise capacity.
†The hazard ratio is for each 1-point increase in the BODE score.


Commentary

Patients with COPD are often undertreated, leading to much preventable morbidity, lost productivity, and economic cost. Identifying at-risk patients could substantially improve outcomes.

The FEV1 is the single best variable to stratify COPD severity. However, it does not accurately predict dyspnea symptoms, exercise tolerance, and mortality. This is because COPD is a systemic disease, and airflow limitation alone does not capture all aspects of disease severity. FEV1 may overestimate exercise tolerance because of dynamic hyperinflation or other nonventilatory limitations. On the other hand, dyspnea may even be absent because the patient has unconsciously narrowed their “envelope” of activity. Cigarette smoking also contributes to other causes of mortality in COPD, including cancer and cardiovascular disease, and is not reflected in the FEV1.

The study by Celli and colleagues introduces the BODE index, which promises to be a very useful prognostic tool. The BODE index was constructed by broadening existing prognostic indicators and adding independent predictors of mortality to the FEV1. It is much more accurate and precise across the spectrum of COPD than any single prognostic factor. The mortality rate was double in the second cohort in this investigation, indicating that the index applied equally to patients with more severe disease. It also predicted the 50% nonrespiratory deaths.

New evidence-based guidelines for COPD emphasize early disease identification and stratification, using office spirometry. This facilitates implementation of exciting new long-acting inhaled bronchodilators, pulmonary rehabilitation, oxygen treatment, and volume reduction surgery.

The BODE index adds another dimension to this effort by identifying at-risk patients, who are most in need of our interventions. It goes beyond FEV1 alone, using easily implemented office tools: the MMRC dyspnea index (1, 2), 6-minute walk, and BMI as a measure of cachexia (3). It also encourages nonpulmonologists, who care for 80% of these patients, to obtain office spirometry and help identify those who are undiagnosed.

Joseph A. Golish, MD
Cleveland Clinic Foundation
Cleveland, Ohio, USA


References

1. Nishimura K, Izumi T, Tsukino M, Oga T. Dyspnea is a better predictor of 5-year survival than airway obstruction in patients with COPD. Chest. 2002;121:1434-40. [PubMed ID: 12006425]

2. Mahler DA, Wells CK. Evaluation of clinical methods for rating dyspnea. Chest. 1988;93:580-6. [PubMed ID: 3342669]

3. Schols AM, Slangen J, Volovics L, Wouters EF. Weight loss is a reversible factor in the prognosis of chronic obstructive pulmonary disease. Am J Respir Crit Care Med. 1998;157:1791-7. [PubMed ID: 9620907]