Dynamic Assessment of the C-Reactive Protein-to-Albumin Ratio Improves Early Prediction of Severe Acute Pancreatitis: A Retrospective Cohort Study.

Background/Objectives: Previous studies have demonstrated the prognostic value of the C-reactive protein-to-albumin ratio (CAR) in acute pancreatitis, but the incremental value of serial measurements remains unclear. We evaluated whether CAR measured at 24 and 48 h provides additional prognostic information beyond admission CAR for predicting severe acute pancreatitis (SAP). Methods: In this retrospective cohort study, 150 consecutive patients with acute pancreatitis were included. CAR was calculated at admission (CAR-T0), 24 h (CAR-T24), and 48 h (CAR-T48). Univariable and multivariable logistic regression, receiver operating characteristic (ROC) analysis, and DeLong's test were used to evaluate prognostic performance. Secondary analyses explored associations with pancreatic pseudocyst, pancreatic ascites, and splanchnic venous thrombosis. Results: Forty-four patients (29.3%) developed SAP. CAR was significantly associated with SAP at all three time points, with CAR-T24 demonstrating the highest predictive performance (AUC 0.874), followed by CAR-T48 (AUC 0.857) and CAR-T0 (AUC 0.829). CAR-T24 showed the highest individual discriminative performance, although its AUC was not significantly higher than that of CAR-T0 (DeLong p = 0.067). In contrast, adding CAR-T24 to the prespecified multivariable model significantly improved discrimination compared with the admission model (AUC 0.890 vs. 0.841; p = 0.016). Dynamic changes in CAR (ΔCAR) were not independently associated with SAP. Admission NLR showed poor predictive performance (AUC 0.578) and was significantly inferior to all CAR time points. Exploratory analyses suggested a potential association between CAR-T24 and splanchnic venous thrombosis; however, given the small number of thrombotic events (n = 10), this finding should be considered preliminary and hypothesis-generating. Conclusions: Serial CAR assessment, particularly at 24 h after admission, provides incremental prognostic value beyond admission CAR alone and may provide additional prognostic information during early clinical reassessment in acute pancreatitis.