Fig. 2

NPAR Analysis with Fitted Curve and ROC Curve for Predicting Postoperative AKI. (A) Relationship between preoperative NPAR values and the risk of postoperative AKI. The horizontal axis represents the preoperative NPAR value, and the vertical axis represents the estimated probability of developing postoperative AKI. The solid red line denotes the fitted logistic regression curve, illustrating the trend of increasing AKI risk with higher NPAR levels. The dotted red lines surrounding the fitted curve represent the 95% confidence intervals, indicating the range of uncertainty around the estimated probability. (B) Receiver operating characteristic (ROC) curves comparing the predictive performance of NPAR, neutrophil percentage, and albumin for postoperative AKI. The diagonal gray line (AUC = 0.5) serves as a reference for a non-informative predictor. Each colored curve corresponds to a specific biomarker: the blue curve represents NPAR (AUC = 0.723, 95% CI: 0.687–0.769), the orange curve represents neutrophil percentage (AUC = 0.705, 95% CI: 0.659–0.747), and the green curve represents albumin (AUC = 0.685, 95% CI: 0.639–0.722). The area under the curve (AUC) values are annotated adjacent to their respective curves to highlight their discriminative power.