Objective To explore the correlation between the systemic immune inflammation index (SII) at admission and severity of neurological deficits, prognosis at 90 days and classification of the Acute Stroke Treatment Org 10172 Trial (TOAST) in patients with acute ischemic stroke (AIS).

Methods A retrospective analysis was conducted on AIS patients who visited the Second People's Hospital of Anhui Province from January to December 2023. Thre laboratory indicators of patients were collected, and SII was calculated. The basic information of patients, National Institutes of Health Stroke Scale (NIHSS) score at admission and modified Rankin Scale (mRS) score at 90 days after the onset of the disease were recorded. The patients were divided into the mild, moderate and severe groups based on the NIHSS score at admission. The basic information and SII among three groups were compared to find their any differences. The patients were divided into the good prognosis group and poor prognosis group according to the mRS Score at 90 days after the onset of the disease, and the difference of SII between two groups was compared. Based on the comprehensive assessment of the patients' clinical symptoms and imaging examination results, they were grouped according to the TOAST classification, and the clinical characteristics and SII levels of each subtype were compared.

Results The SII level in the severe group was higher than that in moderate group (P ＜ 0.05), and the SII level in the moderate group was higher than that in mild group (P ＜ 0.05). After 90 days of follow-up, the SII value and age of AIS patients with poor prognosis were higher than those of AIS patients with good prognosis (P ＜ 0.05). The clinical characteristics and laboratory indicators of patients in different TOAST classification groups were compared. The NHISS scores at admission in the LAA group (large artery atherosclerotic type) and CE group (cardiogenic embolism type) were both higher than those in the SAO group (small artery occlusion type) (P ＜ 0.05).

Conclusions The higher the SII level in AIS patients, the more severe the nerve damage. The older the age of AIS patients and higher the level of SII, the poorer the prognosis of neurological function at 90 days, suggesting that SII can be used as a biomarker for evaluating the severity of the patient's condition and short-term neurological function outcome. In the comparison among various subtypes of TOAST, the degree of neurological deficit at admission in the LAA group and CE group might be more severe than that in SAO group.