Predicting ICU Readmission in Acute Pancreatitis Patients Using a Machine Learning-Based Model with Enhanced Clinical Interpretability

Acute pancreatitis (AP) is a common and potentially life-threatening gastrointestinal disease that places a substantial burden on healthcare systems worldwide. ICU readmissions among patients with AP remain frequent, especially in severe or recurrent cases, with rates exceeding 40%. Timely identification of patients at high risk for readmission is critical for guiding clinical decision-making and improving outcomes. In this study, we used the MIMIC-III database to identify ICU admissions for AP based on standardized diagnostic codes. We implemented a structured preprocessing pipeline that included missing data imputation, correlation analysis, and hybrid feature selection. Specifically, we applied Recursive Feature Elimination with Cross-Validation (RFECV) and LASSO regression, supported by clinical expert review, to reduce an initial set of over 50 variables to 20 key predictors encompassing demographics, comorbidities, laboratory tests, and interventions. To address class imbalance, the Synthetic Minority Over-sampling Technique (SMOTE) was incorporated within a stratified five-fold cross-validation framework to maintain balanced training and unbiased evaluation. Six machine learning models--Logistic Regression, k-Nearest Neighbors, Naive Bayes, Random Forest, LightGBM, and XGBoost--were developed and optimized through grid search. Model performance was assessed using standard metrics including AUROC, accuracy, F1 score, sensitivity, specificity, Positive Predictive Value (PPV), and Negative Predictive Value (NPV). XGBoost achieved the best performance, with an AUROC of 0.862 (95% CI: 0.800-0.920) and accuracy of 0.889 (95% CI: 0.858-0.923) on the test set. An ablation study demonstrated the importance of each selected feature, as removing any one led to a reduction in model performance. Furthermore, SHAP (SHapley Additive exPlanations) analysis was conducted to enhance interpretability. Platelet count, age, and peripheral oxygen saturation (SpO2) were identified as major contributors to readmission prediction. Overall, this study shows that ensemble learning, informed feature selection, and class imbalance handling can improve prediction of ICU readmission risk in patients with AP. These findings may support the development of more targeted post-discharge interventions to reduce preventable readmissions.