Biomarkers of systemic inflammatory status as predictors of delayed cerebral ischemia after subarachnoid hemorrhage

Background: Inflammatory biomarkers and derived indexes have been reported as useful prognostic tools in subarachnoid hemorrhage (SAH) to predict risk of vasospasm, delayed cerebral ischemia (DCI) or death. This study aimed to assess the prognostic value of platelet characteristics, the systemic inflammation index (SII), systemic inflammation response index (SIRI), neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR) and mean platelet volume-to-platelet ratio (MPV:PLT) in patients with aneurysmal subarachnoid hemorrhage. Methods: This was a retrospective cohort study that included 309 adult patients with SAH admitted to the ICU of a tertiary care teaching hospital in Cali, Colombia between 2011 and 2022. Plasma inflammatory biomarkers were measured in patients up to 14 days after SAH. Platelet characteristics trajectory plots by occurrence of DCI were produced to look for trend changes in the first days after SAH that could suggest and underlying pathophysiologic mechanism useful for prediction of this outcome. Odds ratios with 95% confidence interval were calculated for all indexes and ratios in the first three days after SAH using the originally reported cut-off points for its association with DCI, vasospasm, favorable modified Rankin scale score (0-3) and death. The prognostic value of the indexes was assessed through area under the receiver operating characteristic curves (AU-ROC). Results: 309 patients were included in this study (mean age 58.3 years, 68% women). DCI was detected in 137 patients; 44.3%. Vasospasm was detected in 111; 35.9%. During the hospitalization rebleeding occurred in 54 patients (17.5%), hydrocephalus in 107 patients (34.6%) and cerebral ischemia in 77 patients (24.9%). For the cut-off points of SII >1.92, SIRI>3.2, NLR>4, LMR<2, and PLR>145 during the first three days after admission we did not find association with DCI, vasospasm, neurologic outcome or death. The AU-ROC estimates of these indexes did not surpass a pre-stablished usefulness threshold of 75% and thus no new cut-off points were proposed. Conclusions Previously reported results of the prognostic value of inflammatory indexes and biomarkers in patients with SAH or other cerebrovascular diseases were not reproducible in this cohort of patients with aneurysmal subarachnoid hemorrhage. Our findings call into question the reproducibility and applicability of proposed prognostic biomarkers and indexes and should prompt efforts to verify their value in clinical settings, as well as prompt efforts to identify the best prognostic tools available in these patients.