Abstract DP116: Hematoma–Immune Interactions: Lymphocyte Percentage as an Independent Prognostic Marker Enhanced by Imaging in ICH

Background: Spontaneous intracerebral hemorrhage (ICH) is the most devastating stroke subtype. Early prediction of functional outcomes is critical for personalized treatment. Immune-inflammatory responses, particularly T cell–mediated adaptive immunity, contribute to secondary brain injury via hematoma-related inflammation, BBB disruption, and perihematomal edema (PHE). While most studies focus on total leukocyte or neutrophil counts, the prognostic significance of specific T-cell subsets remains unclear, especially when integrated with quantitative imaging metrics. This study evaluated the prognostic value of peripheral % lymphocyte versus individual T-cell subsets (CD3 + , CD4 + , CD8 + ) and their interaction with hematoma/edema burden in predicting short-term functional outcomes after ICH. Methods: We retrospectively analyzed 228 ICH patients (165 males; ≤45 years: n=153). Admission blood samples measured CD3, CD4, CD8 counts, CD4/CD8 ratio, and lymphocyte %. CT quantified hematoma and edema volumes; PHE index and grades were calculated. Discharge NIHSS and mRS scores were recorded. Associations between immune markers, imaging parameters, and outcomes were assessed using multivariate regression, subgroup, and mediation analyses. Results: Lymphocyte% correlated inversely with edema volume (r=−0.25) and both mRS and NIHSS at discharge (r=−0.40, all P <0.05), and remained an independent protective predictor after adjusting for age, sex, hematoma/edema volumes, surgery, and infection (OR=0.924, 95% CI 0.883–0.967, P =0.001). It outperformed individual T-cell subsets. CD4 count showed significant associations with outcome ( P <0.05). Subgroup analyses revealed stronger associations in non-large hematomas, sex-specific patterns (CD4/CD8 in females, lymphocyte % in males), and lobar vs. deep hemorrhage differences. Mediation analysis indicated hematoma volume accounted for 9.2% of the lymphocyte–outcome relationship. Adding lymphocyte % to hematoma volume and age improved AUC for poor-outcome prediction ( P <0.05). Conclusions: Admission lymphocyte % is a robust, independent predictor of short-term functional outcomes after ICH, with additive value beyond hematoma volume and age. Specific T-cell subsets show context-dependent prognostic significance, underscoring complex immune–imaging–outcome interactions. These findings support incorporating lymphocyte % into early risk stratification and highlight the potential of immune-modulating strategies in ICH management.