Association and Comparative Analysis of Four Inflammatory Indices With 90‐Day Outcomes in Acute Ischemic Stroke Patients Treated With Intravenous Thrombolysis

OBJECTIVE: To investigate and compare the associations of the systemic immune-inflammation index (SII), the systemic inflammation response index (SIRI), the platelet-to-lymphocyte ratio (PLR), and the neutrophil-to-lymphocyte ratio (NLR) with 90-day functional outcomes in AIS patients treated with IV rt-PA., with particular attention to their nonlinear relationships and threshold effects. METHODS: Note that 503 AIS patients who received intravenous thrombolysis with alteplase (rt-PA) were consecutively enrolled, and clinical information along with laboratory data were collected. ROC curve analysis was conducted to determine the optimal cut-off value of SII, PLR, NLR, and SIRI. Multivariate analysis was included for variables with p < 0.05 in univariate analysis. The restricted cubic spline (RCS) curve illustrates the nonlinear relationship between SII, PLR, NLR, SIRI, and the 90-day unfavorable outcomes. RESULTS: A total of 503 patients were included. According to multivariate logistic regression analysis, admission NIHSS scores (OR = 1.156, 95% CI: 1.049-1.274), albumin (OR = 0.875, 95% CI: 0.774-0.989), and SII (OR = 1.004, 95% CI: 1.001-1.006) were independent indicators of unfavorable outcomes at 90 day after intravenous thrombolysis (p < 0.05). The ROC analysis showed that an SII cutoff value of 1268.00 could predict poor 90-day outcomes with a sensitivity of 61.58% and a specificity of 92.02%. The AUC was 0.764 (95% CI 0.677-0.852, p < 0.05). Pairwise comparison using the DeLong test revealed that SII and NLR demonstrated comparable discriminative ability (p = 0.392), and both significantly outperformed PLR (SII vs. PLR: p = 0.001; NLR vs. PLR: p = 0.006). No significant difference was detected between SII and SIRI (p = 0.709) or between NLR and SIRI (p = 0.211). SII showed the most consistent independent association in multivariable analysis (OR = 1.004, 95% CI: 1.001-1.006). The RCS curve illustrates the nonlinear relationship between SII, PLR, NLR, SIRI, and the 90-day unfavorable outcomes. CONCLUSIONS: Among the inflammatory indices studied, SII showed the strongest association with 90-day unfavorable outcomes in this cohort. Our findings suggest a potential role of systemic inflammation in patient prognosis post-thrombolysis, warranting further prospective validation.