Systemic Inflammatory Response Index (SIRI) Among Patients With Sepsis: A Retrospective Observational Study

TL;DR

This study evaluates the Systemic Inflammatory Response Index (SIRI) in sepsis patients and finds a weak negative correlation with the SOFA score.

Contribution

The study introduces and evaluates SIRI as a new composite biomarker for sepsis and explores its association with SOFA scores.

Findings

SIRI values were higher in males compared to females.

A weak negative correlation was found between SIRI and SOFA scores at admission.

ALC and AMC values were within normal ranges, while ANC was elevated.

Abstract

Background and objectives: Worldwide, sepsis and multiorgan dysfunction syndrome (MODS) are major health issues. The Sequential Organ Failure Assessment (SOFA) score is used to assess the severity of illness in patients with life-threatening conditions. A new composite biomarker for sepsis is the Systemic Inflammatory Response Index (SIRI). It is based on three metrics: absolute neutrophil count (ANC), absolute lymphocyte count (ALC), and absolute monocyte count (AMC). The aim of this study was to analyze and evaluate the SIRI of sepsis patients of both sexes. We also checked the association between the subjects' SIRI and SOFA scores at admission.

Methods: This study was conducted retrospectively at the Kalinga Institute of Medical Sciences (KIMS), Bhubaneswar, India, between August 2024 and July 2025. This study comprised adult patients of both sexes who met Sepsis-3 criteria. To calculate SIRI, we documented their ANC, ALC, and AMC. On days 1, 3, and 7, we calculated their SOFA scores. The Wilcoxon and chi-square tests were used to evaluate the continuous and categorical variables, respectively. To examine the association between the individuals' SIRI and their SOFA score on the first day, we employed the Spearman correlation. For data analysis, R software (version 4.3.2, R Foundation for Statistical Computing, Vienna, Austria) was utilized.

Results: A total of 2008 patients were analyzed in this study. Their median age was 61.0 (53.0-68.0) years. There were 1170 (58.27%) males. The average hospital stay was 11.0 (9.0-15.0) days, and 1569 (78.14%) subjects had MODS. The median ANC values for female and male subjects were 12.73 (10.41-15.28) x 109/L and 12.42 (10.22-15.95) x 109/L, respectively. The median ALCs of female and male subjects were 1.16 (0.79-1.83) x 109/L and 1.29 (0.83-1.91) x 109/L, respectively. The median AMCs of female and male subjects were 0.49 (0.33-0.71) x 109/L and 0.59 (0.40-0.80) x 109/L. The median SIRI values of female and male subjects were 5.11 (4.03-6.29) x 109/L and 5.55 (4.26-6.88) x 109/L. The median SOFA scores for female and male subjects at admission were 4.0 (2.0-6.0) and 5.0 (3.0-8.0), respectively. There was a negative correlation between SOFA score at day 1 and SIRI (r = -0.078, p < 0.001).

Conclusions: The ANC values were above the normal limits. But the ALC and AMC values were within the normal range. The hematological parameters of the male and female subjects were comparable. Male participants, however, had higher SIRI and SOFA scores. The SOFA score and the SIRI had a weakly negative association. A single-centric study design, a small sample size, and missing information on antibiotic use, daily fluid consumption, urine output, concomitant medications, comorbidities, and renal, hepatic, diabetic, and hemodynamic parameters prevent our study findings from being generalized.

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