ABSTRACTBackground and PurposeThe inflammatory burden index (IBI) is a novel composite biomarker designed to assess systemic inflammation, but its prognostic value in large‐artery atherosclerosis (LAA) ischemic stroke remains unestablished. We evaluated IBI's association with 1‐year clinical outcomes in LAA stroke patients.MethodsIn this multicenter prospective study, 2815 LAA stroke patients were assessed for mortality, recurrence, dependency (mRS 3–5), and poor functional outcome (mRS 3–6). Multivariable‐adjusted Cox/logistic models analyzed associations between admission IBI and outcomes. Comparative analyses used ROC curves with DeLong's test and quantified incremental value through net reclassification improvement (NRI)/integrated discrimination improvement (IDI).ResultsMedian IBI was 11.2 (IQR 5.4–25.8). At 1 year, outcomes included: mortality 3.2% (n = 90), recurrence 8.3% (n = 235), dependency 11.5% (n = 324), and poor outcome 14.7% (n = 414). Elevated IBI levels were significantly associated with increased all‐cause mortality (hazard ratio [HR] 4.26; 95% confidence interval [CI], 1.76–10.33), stroke recurrence (HR 1.63; 95% CI, 1.10–2.42), dependency (odds ratio [OR] 1.81; 95% CI, 1.24–2.66), and poor functional outcome (OR 2.41; 95% CI, 1.69–3.43). IBI demonstrated superior discrimination for dependency (AUC 0.86) and poor outcome (AUC 0.86) compared with NLR, PLR, SII, and CRP (all p < 0.01 by DeLong's test). Adding IBI to conventional risk models significantly improved reclassification and discrimination for all the clinical outcomes.ConclusionsElevated admission IBI independently predicts 1‐year mortality, recurrence, dependency, and functional impairment in LAA stroke. IBI provides significant prognostic value beyond conventional inflammatory markers and clinical risk models.