Background We have previously reported that distance walked on the Incremental shuttle walking test (ISWT) can be substituted for the 6 min walking distance (6MWD) as the exercise (“E” component) of the BODE index (ERS 2009). This study examines 5 year survival in a cohort of patients with COPD and examines the validity of the modified BODE index as an independent predictor of survival in COPD.
Method Hospital records of 1127 patients with COPD referred to PR (mean (SD) FEV1 46.1 (16.2)% predicted, age 68.4 (9.0) years) were examined to assess 5-year survival. A multivariate cox proportional hazards model including the variables gender, age, pack years, FEV1, FVC, BMI, MRC dyspnoea score and ISWT was used to identify independent factors predicting all cause mortality. A BODE score was then assigned to 626 patients with sufficient data for analysis. Cut-off points for the ISWT quartiles were as follows:<80 m=3, 80–149 m=2, 150–249 m=1, >250 m=0. Cox regression was used to predict hazard ratios for the modified BODE index, adjusted for the independent prognostic factors identified by initial analysis. Kaplan–Meier analysis of survival by quartile of the BODE index was then performed and compared with the log rank test.
Results Overall 5-year survival was 41.9%. Three of the four factors in the BODE index (BMI, exercise capacity, and MRC dyspnoea) were statistically significant independent predictors of survival whilst the fourth, FEV1% predicted was of borderline significance (p=0.08). In addition age and pack years smoked were also independent prognostic factors. The mean (SD) BODE index was significantly higher in patients who had died at 5 years (5.9(2.2)) than those that had survived (4.8(2.2)), p<0.0001. The modified BODE index was a significant predictor of death even corrected for age and pack years smoked (adjusted hazard ratio (95% CI) 1.26 (1.17 to 1.35), p<0.0001). Kaplan–Meier survival analysis confirmed that each quartile increase in the BODE index was associated with increased mortality (p<0.0001) (Abstract S72 Figure 1).
Conclusion The BODE index using the ISWT as the exercise component, is a useful tool for predicting survival in patients with COPD.