Identification of relevant variables and construction of a multidimensional index for predicting mortality in COPD patients

Abstract

Background and objective: The Body mass index, airflow Obstruction, Dyspnea, and Exercise (BODE) index is a well-known metric for chronic obstructive pulmonary disease (COPD), but it is inadequate for predicting mortality. This study proposed a new index that combines inspiratory muscle training with the BODE index and verified its ability to predict mortality in patients with COPD. Methods: Cox regression identified predictors of mortality, which were then included in the new index. The receiver operating characteristic (ROC) curve verified the ability of the new index to predict mortality. The Kaplan-Meier curves compared the survival rates of patients with different scores on the new index. Results: Among the 326 patients, 48 died during follow-up (1–59 months). Cox regression showed that the fat-free mass index (FFMI), forced expiratory volume in one second/the predicted value (FEV1%), modified Medical Research Council (mMRC) score, six-minute– walk test (6MWT) distance, and maximal inspiratory pressure were predictors of mortality (P<0.05); these variables were included in the FODEP index. The AUC of the FODEP index (0.860, 95% CI: 95% CI: 0.817–0.896) was greater than that of the BODE index (0.778, 95% CI: 0.729–0.822). The Kaplan-Meier curves suggested that as the FODEP score increased, so did the risk of morality in patients with COPD. The cumulative survival in the group with the highest FODEP-value was significantly lower than that in the other groups (P<0.01). Conclusion: The FODEP index was more effective than the BODE index at predicting the risk of mortality in patients with COPD.