The Predictive Value of Nomogram Model Based on Neutrophil-to-Lymphocyte Ratio (NLR) and Prothrombin Time-International Normalized Ratio (PT-INR)-to-Albumin Ratio (PTAR) for Early Bacterial Intra-Abdominal Infection After Orthotopic Liver Transplantation

Purpose: To identify risk factors for bacterial intra-abdominal infections (IAIs) after orthotopic liver transplantation (OLT) and establish a nomogram prediction model based on preoperative neutrophil-to-lymphocyte ratio (NLR) and preoperative prothrombin time-international normalized ratio (PT-INR)-to-albumin ratio (PTAR). Patients and Methods: We retrospectively analyzed 261 patients who received OLT between January 2020 and April 2024 in Beijing Friendship Hospital. Independent risk factors for bacterial IAIs within 30 days postoperatively were identified by logical regression analysis. The area under the receiver operating characteristic (ROC) curve (AUC) was calculated to evaluate the predictive performance of NLR and PTAR as well as the nomogram model based on them. Hepatic function was evaluated using the Child–Turcotte–Pugh (CTP) score and the Model for End-Stage Liver Disease (MELD) score. Results: Fifty patients (19.2%, 50/261) developed postoperative bacterial IAIs. The majority of the 66 isolated strains were gram-negative (63.6%). Most infections (74.0%, 37/50) occurred within two weeks postoperatively. Multivariate logistic regression analysis identified preoperative NLR, preoperative PTAR, acute physiology and chronic health evaluation II (APACHE II) score, and biliary leakage as independent risk factors. A nomogram-based prediction model was constructed utilizing the identified independent risk factors. Internal validation was conducted through the bootstrap method. The Hosmer–Lemeshow test indicated no significant deviation from the goodness-of-fit (χ 2 = 7.349, P = 0.499 > 0.05). The calibration curve indicated excellent concordance between predicted and observed outcomes. The nomogram exhibited strong discriminative capability, evidenced by a C-index of 0.900 (95% CI: 0.828– 0.972) and an AUC of 0.912 (95% CI: 0.864– 0.960) for predicting abdominal infection, with an optimal diagnostic threshold of 0.221 (95% CI: 0.125– 0.265). Decision curve analysis revealed a positive net benefit across a wide range of threshold probabilities (0.03– 1.0), indicating the model’s substantial clinical utility. Conclusion: Both the preoperative NLR and the preoperative PTAR are independent risk factors for IAIs within 30 days after OLT. The nomogram model based on NLR and PTAR can effectively predict the occurrence of IAIs after OLT. Keywords: orthotopic liver transplantation, intra-abdominal infection, neutrophil-to-lymphocyte ratio, international normalized ratio-to-albumin ratio, nomogram model