Modified BODE indexes: Agreement between multidimensional prognostic systems based on oxygen uptake

AIM It has been recently shown that the original BODE index has a high degree of correlation with two modified BODE indexes using maximal oxygen uptake expressed either as mL/min/kg (mBODE) or as the percentage predicted (mBODE%). In this study we investigated the agreement between the two modified BODE indexes (mBODE and mBODE%) in patients with stable chronic obstructive pulmonary disease (COPD). METHODS A total of 169 patients with stable COPD were enrolled in this cross-sectional study. Differences between the two mBODE indexes were assessed using kappa coefficients and Bland-Altman plots. One out of every three patients underwent the six-minute walking test to investigate the agreement with the original BODE index. RESULTS Correlations between the two mBODE indexes with each other (r = 0.96, P < 0.001) and with the original BODE index (mBODE r = 0.88, P < 0.001; mBODE% r = 0.93, P < 0.001) were excellent. However, the two mBODE indexes were significantly different from each other (mBODE 5.27 +/- 2.3 versus mBODE% 4.31 +/- 2.5; P < 0.001). The kappa coefficients were significantly lower (entire study group k = 0.5, P < 0.001) for every GOLD stage. The mean difference between the two mBODE indexes was 0.8 +/- 0.6 units. Differences with the original BODE were higher for the mBODE (1.8 +/- 0.9) than for the mBODE% (0.6 +/- 0.8). CONCLUSIONS The new mBODE indexes are highly correlated but significantly different from each other. The differences between the novel indexes deserve further scrutiny.