Systemic Immune-Inflammation Index (SII) as a Predictor of Pressure Injury Risk in Intensive Care Units: A Retrospective Cohort Study

Background Pressure injuries (PIs) are common in intensive care unit (ICU) patients and are associated with increased morbidity, prolonged hospitalization, and elevated healthcare costs. However, reliable biomarkers for early risk stratification remain limited. This study aimed to evaluate whether the Systemic Immune-Inflammation Index (SII), Neutrophil-to-Lymphocyte Ratio (NLR), and Platelet-to-Lymphocyte Ratio (PLR) can predict the risk of PI development in ICU patients. Methods This retrospective cohort study was conducted at Sinop Atatürk State Hospital between January 2023 and June 2024. Adult ICU patients who developed PIs during hospitalization were included. Of the 64 patients, 51 were included in the analysis. Demographics, comorbidities, and laboratory parameters were recorded. SII, NLR, and PLR were calculated at ICU admission and on the day of PI diagnosis. Change ratios and their correlations with time to PI onset were evaluated. Results The mean age of the cohort was 77.6 ± 9.1 years, and 52.9% were female. PIs developed at a mean of 19.4 ± 13 days after ICU admission. Median SII, NLR, and PLR values significantly decreased between admission and diagnosis (all p < 0.001). SII and NLR change ratios showed a significant positive correlation with PI onset time (p = 0.047 and p = 0.011, respectively); PLR did not (p = 0.549). Conclusion Dynamic changes in SII and NLR may reflect systemic inflammation that impairs tissue repair and promotes PI development. Incorporating these markers into risk models could support early detection and prevention. Larger prospective studies are required for validation. Clinical trial number: Not applicable. This study is a retrospective observational analysis and was not registered as a clinical trial.