The diagnostic value of the systemic immune-inflammation index in acute pancreatitis: a retrospective cohort study

Early risk stratification in acute pancreatitis (AP) is essential to guide triage decisions and clinical management. This study aimed to evaluate the prognostic utility of the systemic immune-inflammation index (SII) and neutrophil-to-lymphocyte ratio (NLR) ,readily accessible, inflammation-based biomarkers, in predicting intensive care unit (ICU) admission and in-hospital mortality.

This retrospective cohort study analyzed 308 adult patients diagnosed with AP at a tertiary academic emergency department between January 2024 and December 2025. SII and NLR were calculated from admission complete blood count parameters. The primary outcome was ICU admission, and secondary outcomes included in-hospital mortality. Group comparisons were performed using nonparametric tests. Receiver operating characteristic (ROC) curve analysis was used to evaluate the diagnostic performance of SII and NLR for ICU admission and mortality.

Of the 308 patients included, 4.9% (n=15) required ICU admission and 4.5% (n=14) died during hospitalization. Both SII and NLR values were significantly elevated in patients admitted to the ICU and in those who died compared with their counterparts. For ICU admission, NLR and SII demonstrated an area under the curve (AUC) of 0.856 and 0.831, respectively. For in-hospital mortality, the AUC was 0.894 for NLR and 0.885 for SII. Both indices showed high negative predictive values for adverse outcomes.

Admission-level SII and NLR demonstrated meaningful diagnostic performance for identifying AP patients at risk for ICU admission and in-hospital mortality. As cost-effective and easily derived markers, they offer valuable prognostic insight, potentially enhancing early risk-based triage and clinical intervention strategies in emergency settings.