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COPD is a heterogeneous disease that has systemic manifestations in addition to those resulting from airflow obstruction. While FEV1 is a good predictor of mortality, it correlates less well with dyspnoea and health status. The authors hypothesised that a multidimensional grading system would prove a better predictor of outcomes than FEV1 alone.
In the initial stage of the study 207 patients were retrospectively evaluated. It was established that the four factors best predicting risk of death were body mass index (BMI, B), airflow obstruction (O) as measured by the post-bronchodilator FEV1 (percentage of predicted value), dyspnoea (D) assessed by the modified Medical Research Council (MMRC) score, and exercise tolerance (E) measured by 6 minute walking distance. The variables were graded 0 to 3 (0 or 1 for BMI) and summed to give a total score between 0 and 10. This score was called the BODE index, with higher scores indicating a greater risk of death. The index was then prospectively evaluated in a cohort of 625 patients. The hazard ratio per one point increase in BODE score was 1.34 (1.26 to 1.42, p<0.001) for death from any cause and 1.62 (1.48 to 1.77, p<0.001) for respiratory deaths. The C statistic evaluating the ability of the index to predict death was greater than for the FEV1 alone (0.74 v 0.65).
The BODE index is a new multidimensional grading system for COPD that is a better predictor of death than FEV1. Its usefulness as an indicator of outcome in clinical trials or as a predictor of heath service utilisation remains to be established.