Fig. 2

Receiver operating characteristic (ROC) curve and calibration plot. A ROC curve in the derivation cohort. The area under the receiver operating characteristic curve (AUROC) for the composite index to predict 28-day survival showed 0.76, and the cutoff was 0.19. The positive predictive value (PPV) of the composite index was 0.928, and the negative predictive value (NPV) was 0.316. B Calibration plot in the derivation cohort. The calibration plot demonstrated a perfect fit of the estimated probability of survival to survival probability when the survival probability was higher than 0.6. The gray band showed a 95% confidence interval (CI). C ROC curve in the validation cohort. The AUROC for the composite index to predict 28-day survival showed 0.71. The PPV of the composite index was 0.913, and NPV was 0.251. D Calibration plot in the validation cohort. The calibration plot demonstrated the gap between the survival probability and the estimated probability of survival, especially when the survival probability was low. The gray band showed a 95% CI