Systemic Coagulation-Inflammation Index Predicts Functional Outcomes After Aneurysmal Subarachnoid Hemorrhage: Mediation by Delayed Cerebral Ischemia

The systemic coagulation-inflammation (SCI) index reflects both coagulopathic and inflammatory dynamics. We investigated its association with delayed cerebral ischemia (DCI) and functional outcome in aneurysmal subarachnoid hemorrhage (aSAH), explored the mediation effect of DCI within the chain of events, and evaluated the additive predictive value of SCI index. Consecutive aSAH patients were retrospectively analyzed. Multivariate logistic regression examined associations between SCI index, DCI, and poor six‑month outcome. Causal mediation with four‑way decomposition assessed whether DCI mediates the relationship between the SCI index and functional outcome. Finally, the area under the curve (AUC), net reclassification improvement (NRI) and integrated discrimination improvement (IDI) were calculated to evaluate the additive value. In total, 583 aSAH patients were included. Among them, DCI occurrence was observed in 133 (23.3%) patients, and functional disability was seen in 177 (30.4%) patients. After adjusting for confounding variables, an elevated SCI index was significantly associated with both DCI and poor outcome. Additionally, the effect of SCI index on poor outcome was partially mediated by DCI, as a mediator that accounted for 23.3% of the positive association. Moreover, adding the SCI index to the predictive model improved the AUC from 0.720 to 0.742, with an NRI and IDI of 3.9 and 2.0%, respectively. The SCI index was associated with poor functional outcomes in aSAH, an effect partially mediated by DCI. Besides, the SCI index slightly improved the outcome prediction after aSAH. However, further studies are necessary to validate our findings and explore the mechanisms.