Systemic Inflammatory Indices (SII and SIRI) in 30-Day Mortality Risk Stratification for Community-Acquired
Orkun Eray Terzi1, Gülgün Çetintaş Afşar1, Nazlı Çetin2
1Department of Pulmonology, Bursa Yuksek Ihtisas Training and Research Hospital, 16310 Bursa, Türkiye.
Pathogens (Basel, Switzerland)
|December 31, 2025
Summary
Simple inflammatory markers, Systemic Immune-Inflammation Index (SII) and Systemic Inflammation Response Index (SIRI), show modest prognostic value for community-acquired pneumonia (CAP) mortality. They offer limited adjunctive information when combined with traditional scoring systems.
Area of Science:
- Pulmonology
- Critical Care Medicine
- Biomarker Research
Background:
- Community-acquired pneumonia (CAP) is a significant global health concern, driving morbidity and mortality.
- Effective early risk assessment for CAP necessitates accessible and cost-effective biomarkers.
- Existing severity scores like CURB-65 and PSI are established but may benefit from complementary indicators.
Purpose of the Study:
- To evaluate the prognostic performance of the Systemic Immune-Inflammation Index (SII) and Systemic Inflammation Response Index (SIRI) in hospitalized CAP patients.
- To compare the predictive accuracy of SII and SIRI against established CAP severity scores.
- To determine if SII and SIRI enhance mortality prediction when used alongside CURB-65 and PSI.
Main Methods:
- Retrospective analysis of 240 adult patients hospitalized with CAP.
- Calculation and comparison of SII and SIRI values in relation to 30-day all-cause mortality.
- Logistic regression and receiver operating characteristic (ROC) analyses were employed for performance evaluation.
- Correlation analysis with conventional inflammatory markers (C-reactive protein, procalcitonin) was performed.
Main Results:
- The 30-day mortality rate was 15.4%.
- Non-survivors had significantly higher SII (p=0.043) and a trend towards higher SIRI (p=0.072).
- SII and SIRI demonstrated weak positive correlations with C-reactive protein and procalcitonin.
- CURB-65 and PSI showed superior discriminative ability compared to SII and SIRI.
- SII and SIRI did not significantly improve mortality prediction beyond established scores.
Conclusions:
- The Systemic Immune-Inflammation Index (SII) and Systemic Inflammation Response Index (SIRI) provide modest prognostic information in CAP.
- These hematology-based indices may offer limited, clinically relevant adjunctive value when integrated with traditional scoring systems.
- Further research could explore optimal integration strategies for these systemic inflammation markers in CAP risk stratification.
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