Immune-inflammatory profiles and disease severity in pulmonary tuberculosis complicated by central nervous system tuberculosis.

OBJECTIVE: To compare peripheral blood immune-inflammatory profiles between patients with pulmonary tuberculosis complicated by central nervous system tuberculosis (PTB + CNS-TB) and those with pulmonary tuberculosis alone (PTB), and to identify laboratory parameters associated with disease severity in PTB + CNS-TB. METHODS: This retrospective study included 4,829 inpatients with tuberculosis (January 2018-March 2026), comprising a PTB group (n = 4,578) and a PTB + CNS-TB group (n = 251). Propensity score matching (1:4) was performed using sex, age, body mass index, albumin, and hemoglobin, yielding 246 PTB + CNS-TB patients and 954 matched PTB controls. PTB + CNS-TB cases were further stratified by Medical Research Council (MRC) grading (Grade I: n = 165; Grades II-III: n = 86). Covariate-adjusted analyses with FDR correction were used to screen severity-associated parameters; LASSO and Firth's logistic regression were applied to identify mutually independent factors and to construct a severity assessment model. RESULTS: After matching, PTB + CNS-TB patients exhibited a distinct bidirectional pattern characterized by reduced peripheral lymphocyte counts and lower peripheral T-cell counts (CD3+, CD4+, and CD8+) and CD45+ lymphocytes counts, alongside increased neutrophil-related inflammatory indices (including neutrophil count, neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, and systemic immune-inflammation index) (all P < 0.05). Within the PTB + CNS-TB cohort, severe disease was associated with higher white blood cell and neutrophil-related measures (notably NEU% and NLR) and more pronounced cerebrospinal fluid (CSF) abnormalities, particularly elevated CSF protein and decreased CSF chloride, whereas peripheral T-cell subset parameters did not differ significantly by severity. Multivariable modeling identified CSF protein, NEU%, and albumin as mutually independent factors associated with severe disease. A combined model including these three markers showed good internal discrimination (AUC = 0.772; bootstrap-corrected AUC = 0.767) and calibration. CONCLUSIONS: PTB + CNS-TB is associated with reduced peripheral lymphocyte/T-cell subset counts accompanied by heightened a neutrophil-predominant inflammatory profile. Among PTB + CNS-TB patients, disease severity shows a closer association with neutrophil-related indices and routine CSF parameters, particularly CSF protein, than with peripheral T-cell subset counts. A model incorporating NEU%, CSF protein, and albumin may aid in severity assessment.