ORIGINAL RESEARCH article
Front. Med.
Sec. Intensive Care Medicine and Anesthesiology
Novel pneumonia score based on Systemic Immune-inflammation Index and Prognostic Nutritional Index in elderly patients
Provisionally accepted
- The Affiliated People’s Hospital of Ningbo University, Ningbo, China
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Background: The mortality rate for elderly patients with community-acquired pneumonia (CAP) admitted to intensive care units (ICU) is high. The combination assessment of Systemic Immune-inflammation Index (SII) and Prognostic Nutritional Index (PNI) can provide a more comprehensive evaluation of the patient's immune response, systemic inflammatory burden, and nutritional metabolic status.. Methods: From the Medical Information Mart for Intensive Care IV database (MIMIC-IV, version 3.1), we selected 12457 patients with CAP admitted to the ICU. After exclusions, 634 patients were included and randomly split into training (n=444, 70%) and internal validation (n=190, 30%). Meanwhile, an independent external validation cohort comprised 149 patients admitted to The Affiliated People's Hospital of Ningbo University (January 2024 - March 2025) was collected. Optimal thresholds for SII and PNI were derived from receiver operating characteristic (ROC) analysis in the training cohort, which were subsequently used to calculate the SII-PNI score. Model performance was evaluated through net reclassification improvement, decision-curve analysis, logistic regression analysis, and Kaplan-Meier curves. Validation was performed in internal and external cohorts to assess the model's predictive value in geriatric CAP patients. Results: ROC analysis determined the optimal cutoff values for SII (2030.28; AUC = 0.573, 95% CI 0.517 - 0.628, p < 0.05) and PNI (29.07; AUC = 0.638, 95% CI 0.584 - 0.692, p < 0.001) in the training cohort. The SII-PNI scoring model was subsequently developed using these thresholds and demonstrated predictive value for 30-day in-hospital mortality [OR: 2.19 (95% CI: 1.62-2.95), p < 0.001]. Kaplan-Meier survival analysis confirmed consistent prognostic performance across all cohorts, that patients with a score of 2 on the SII-PNI scale had significantly higher 30-day mortality compared to those with scores of 0 or 1 (p < 0.05). Conclusion:The SII-PNI may serve as a adjunct for evaluating the 30-day mortality rate among elderly ICU patients admitted with CAP.
Keywords: Community-acquired pneumonia, systemic immune-inflammation index, SII, Prognostic nutritional index, PNI, Mortality
Received: 05 Sep 2025; Accepted: 06 Nov 2025.
Copyright: © 2025 Chen, Zhao, Liang, Zhou, Wang and Yu. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence:
Xiaofei Chen, rmchenxiaofei@nbu.edu.cn
Wanjun Yu, nbyuwanjun@163.com
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