Association between the systemic inflammation response index and serum uric acid in acute traumatic brain injury: a cross-sectional study.

Background: Traumatic brain injury (TBI) involves systemic inflammation, oxidative stress, and metabolic disturbances. The systemic inflammation response index (SIRI) and serum uric acid (UA) are both linked to inflammatory and oxidative processes, but their relationship in acute TBI is unclear. Objective: To examine the association between SIRI and serum UA in adults with acute TBI, including potential nonlinear patterns and differences by sex and injury severity. Methods: This retrospective cross-sectional study included 1,930 adults with CT-confirmed acute TBI admitted between March 2018 and April 2024. Laboratory data were collected within 24 h of admission. SIRI was calculated as neutrophil × monocyte/lymphocyte. Multivariable linear regression, generalized additive models, and piecewise linear regression were used to assess the association between SIRI and UA. Subgroup analyses were conducted by sex and Glasgow Coma Scale (GCS) category. Results: Higher SIRI was independently associated with higher UA levels. In the fully adjusted model, each 1-unit increase in SIRI corresponded to a 0.88 μmol/L increase in UA ( Conclusion: Higher SIRI was associated with increased serum UA in acute TBI, suggesting a link between systemic inflammation and purine metabolism after injury. This relationship may be stronger in females and in severe TBI. Further longitudinal multicenter studies are needed.