Abstract:Aim To analyze the dynamic changes of the atherogenic index of plasma (AIP) during the course of severe acute pancreatitis (SAP) and its predictive efficacy for patient prognosis. Methods We collected and analyzed clinical data from 150 patients with SAP at 363 Hospital from June 2020 to June 2024, and patients were grouped based on their prognosis outcomes during the 28-day follow-up period after admission, with 112 patients assigned to the survival group and 38 patients to the mortality group. Repeated-measures analysis of variance (ANOVA) was used to compare changes in triglyceride (TG), high density lipoprotein cholesterol (HDLC), AIP and inflammatory markers between the two groups at baseline (T0), day 5 post-treatment (T5), and day 10 post-treatment (T10). Multiple linear regression analysis was performed to examine the relationship between AIP and inflammatory markers at different time points; Logistic regression models were used to analyze the independent association between AIP and SAP patient mortality risk at different time points; Receiver operating characteristic (ROC) curve analysis was used to evaluate the relationship between AIP, TG, HDLC, inflammatory markers and SAP patient mortality risk at different time points;Restricted cubic spline (RCS) analysis was used to analyze the relationship between AIP and SAP patient mortality risk; Multidimensional stratified analysis was used to analyze the association between AIP levels and SAP patient mortality risk; Kaplan-Meier survival curve analysis was used to analyze SAP patients' survival rates; Subgroup analysis was performed to examine the association between AIP and SAP mortality risk at T5 and T10 in patients with different etiologies. DeLong's test was further used to analyze the predictive efficacy of AIP for SAP after excluding lipidogenic patients. Results The age, multiple organ failure, white blood cell count (WBC), acute physiological and chronic health score Ⅱ (APACHEⅡ), and sequential organ failure assessment (SOFA) scores of patients in the death group were significantly higher than those in the survival group.Conversely, albumin (ALB), total cholesterol (TC), and low density lipoprotein cholesterol (LDLC) levels were significantly lower in the death group than those in the survival group (P<0.05). In the survival group, TG, AIP, C-reactive protein (CRP), procalcitonin (PCT), and interleukin-6 (IL-6) levels decreased sequentially at time points T0, T5, and T10, whereas in the death group, AIP, CRP, PCT, and IL-6 exhibited an initial increase followed by a decline. HDLC levels increased in the survival group but decreased first and then increased in the death group, with statistically significant differences (P<0.05). Repeated measures ANOVA on TG, HDLC, AIP, CRP, PCT, and IL-6 in both groups revealed statistically significant differences in time, between groups, and time×group interaction (P<0.05). At T0, T5, and T10, AIP showed a positive linear correlation with CRP, PCT and IL-6 (P<0.05). Logistic regression analysis indicated that AIP at stages T5 and T10 was independently associated with mortality risk in SAP patients (P<0.05). ROC curve analysis revealed that AIP exhibited optimal predictive efficacy at T5 (AUC:0.2,5%CI:0.873~0.965) and T10 (AUC:0.1,5%CI:0.914~0.993), with the highest predictive efficacy at T10, accompanied by the highest sensitivity (99.5%) and accuracy (88.7%). RCS analysis indicated a nonlinear dose-response relationship between AIP and SAP mortality risk at T5 and T10 (P<0.05). Multidimensional stratified analysis revealed associations between AIP and SAP mortality risk at T5 and T10 in subgroups with APACHEⅡ≥20, SOFA≥8, CRP≥200 mg/L, PCT≥10 mg/L, and IL-6≥300 ng/L, with higher mortality risk observed in SAP patients with organ failure. Survival curve analysis revealed statistically significant differences between the AIP>0.20 group and the AIP≤0.20 group at T5 (χ2=6.437, P<0.001) and between the AIP>0.10 group and the AIP≤0.10 group at T10 (χ2=5.831, P<0.001). Subgroup analysis revealed independent associations between AIP and mortality risk at T5 and T10 in different etiologies, with more pronounce correlations observed in the high AIP level group, and both demonstrated good discriminatory ability. After excluding lipid-derived patients, ROC curve analysis indicated that AIP still retained predictive efficacy in non-lipid-derived SAP patients, with higher predictive performance at T10 (AUC:0.8,5%CI:0.880~0.971). Conclusions AIP exhibits dynamic changes during the disease course in SAP patients, At T5 and T10, AIP shows independent correlation with mortality risk, and exhibits linear correlations with CRP, PCT, and IL-6. The predictive efficacy of AIP is highest at T10, and it maintains robust predictive performance even after excluding lipid-derived patients. Incorporating dynamic AIP monitoring into clinical evaluation systems helps identify high-risk patients at an early stage and improves the efficacy of prognosis assessment.