Clinical and Biochemical Determinants of the Systemic Inflammation Response Index During Vancomycin Therapy

Vancomycin (VAN) is the standard of care for Gram-positive infections. The systemic inflammation response index (SIRI) has been associated with infections and sepsis across various clinical settings; however, the correlates and determinants of the SIRI during VAN therapy remain unexplored. This retrospective cross-sectional study aimed to identify the determinants of the SIRI among adults treated with VAN.

Medical records of 299 patients who received VAN were analyzed consecutively. Prevalence rates were calculated; Spearman's correlation and regression models were employed to evaluate associations; risk assessment was conducted using prevalence ratios and odds ratios; diagnostic potential was assessed using receiver operating characteristic curves.

The SIRI was significantly higher in intensive care unit (ICU) patients than in non-ICU patients receiving VAN therapy (p < 0.0001). Age, blood pressure, creatinine, Na⁺, CO₂, albumin, aspartate transaminase (AST), gamma-glutamyl transferase (GGT), bilirubin, coefficient of variation in red cell distribution width (RDW-CV), and platelet count were significantly and differentially correlated with the SIRI. In the adjusted analysis, ICU requirement emerged as the strongest independent predictor of SIRI, with ICU patients showing a 2.13-fold higher SIRI(p < 0.0001). Moreover, the prevalence of ICU requirement was 1.61 times higher in individuals with increased SIRI (p = 0.0018), whose odds of ICU requirement were 2.16 times higher (p = 0.0016). The SIRI also demonstrated moderate discriminatory ability, with the highest performance observed in patients younger than 50 years (area under the curve [AUC] = 0.731, p = 0.0001).

The SIRI is a novel and cost-effective marker that is correlated with distinct demographic and clinical variables and independently associated with ICU requirement in VAN-treated patients and may aid in the risk stratification and management of this vulnerable patient cohort.