Prognostic role of admission neutrophil-to-lymphocyte ratio in acute ischemic stroke: a systematic review and updated meta-analysis of 31,835 patients

Objective To evaluate the association of admission neutrophil-to-lymphocyte ratio (NLR) with functional outcomes, intracranial hemorrhage (ICH), and mortality in patients with acute ischemic stroke (AIS).Methods We searched PubMed, Scopus, Web of Science, Cochrane CENTRAL, and Embase from inception until December 17, 2024. Studies examining admission NLR as a predictor for functional outcomes, ICH, and mortality in AIS patients were included. A meta-analysis was performed using pooled odds ratios (ORs) with 95% confidence intervals (CIs). Subgroup analyses were conducted based on treatment modality, time of measurement, hemorrhage type, and ethnicity. Heterogeneity was assessed using I2 statistics, and publication bias was evaluated using Egger’s test.Results Sixty observational studies (33,049 patients), including 59 cohort studies and one cross-sectional study, were included. Higher admission NLR was significantly associated with unfavorable functional outcomes (OR: 1.10, 95% CI: [1.07, 1.14]), ICH (OR: 1.06, 95% CI: [1.03, 1.09]), and mortality (OR: 1.06, 95% CI: [1.04, 1.08]). Subgroup analysis indicated that NLR was associated with poor outcomes in AIS patients receiving mechanical thrombectomy and intravenous thrombolysis.Conclusion Admission NLR is significantly associated with unfavorable functional outcomes, ICH, and mortality in AIS patients. Its predictive value remained evident in the MT and Asian subgroups; however, the association with unfavorable functional outcomes was not significant in the non-Asian subgroup, and the association with mortality in the IVT subgroup was also not significant. Given its accessibility and cost-effectiveness, NLR holds promise as a routine biomarker for stroke prognosis.