ABSTRACT

The Systematic Inflammatory Index (SII) is a readily available score combining combining three readily available laboratory markers: Plathelets, neutrophils and lymphocytes as a measure of immune activation. We aimed to investigate the ability of SII to predict hospital length of stay (LOS) in a diverse patient population. We conducted a retrospective cohort study using the hospital records  between 2019 and 2022. Patients aged 18 years or older admitted for any medical or surgical diagnosis were included. The primary outcome was hospital LOS in days. We extracted baseline SII, along with demographics, comorbidities, and admission diagnoses. We stratified patients by diagnosis categories and analyzed the association between SII and LOS using multivariable linear regression, adjusting for potential confounders. We included 135 patients in the analysis. The median SII was 7.13 (IQR 4.18-11.69). Higher SII was significantly associated with longer LOS (β coefficient = 0.10 days per unit increase in SII, p < 0.001). This association remained significant after adjusting for demographics, comorbidities, and diagnosis categories. The strongest predictive value of SII was observed in patients with infectious diagnoses (β = 0.24 days, p < 0.001) and cardiovascular diagnoses (β = 0.18 days, p < 0.001). Subgroup analyses by age and sex showed similar associations between SII and LOS. Our study demonstrates that SII is a readily available and easily interpretable marker that can predict hospital LOS in a diverse patient population. SII may be particularly useful for identifying patients at risk for prolonged hospital stays, especially those with infections and cardiovascular diagnoses, regardless of age or sex. This information could help optimize resource allocation, treatment planning, and discharge decisions.

Keywords

Systematic Inflammatory Index, hospital length of stay, prognosis.

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