Prognostic value of the systemic inflammatory index (SII) and systemic inflammatory response index (SIRI) in patients with traumatic spinal cord injury

Purpose The overwhelming inflammatory response plays a critical role in the secondary injury cascade of traumatic spinal cord injury (tSCI). The systemic immune inflammatory index (SII) and systemic inflammatory response index (SIRI) are two novel inflammatory biomarkers. The SII was calculated based on lymphocyte, neutrophil, and platelet counts, while the SIRI was calculated based on lymphocyte, neutrophil, and monocyte counts. Their prognostic value in patients with tSCI remains unclear. Methods Patients with tSCI admitted within 24 h of trauma were retrospectively and consecutively enrolled. Peripheral blood samples were collected on admission. The primary outcome was American Spinal Injury Association Impairment Scale (AIS) grade conversion at discharge. Multivariable logistic regression analysis was performed to determine the relationship between SII and SIRI and AIS grade conversion. We performed receiver operating characteristic curve (ROC) analysis to assess the discriminative ability of SII, and SIRI in predicting AIS grade conversion. Results Among 280 included patients, 77 (27.5%) had improved AIS grade conversion at discharge. After adjustment for confounders, SII was independently associated with AIS grade conversion (per SD, odds ratio [OR], 0.68; 95% confidence interval [CI] 0.47–0.98, p = 0.040), while the association between SIRI and AIS grade conversion was insignificant (per 1 SD, OR, 0.77; 95% CI 0.55–1.08, p = 0.130). The ROC analysis revealed that the SII had the best predictive value for AIS grade conversion (area under curve: 0.608, 95% CI 0.536–0.678). Conclusions Increased SII was independently associated with a decreased likelihood of improved AIS grade conversion.