Objective:

To map serum IL-6 levels across 10 categories of neurological disorders, including traumatic brain injury, metabolic/toxic encephalopathy, and hemorrhagic stroke, and assess its diagnostic performance.

Key Findings:

• Significant heterogeneity in serum IL-6 levels across disease categories (p < 0.001).
• Highest IL-6 levels found in traumatic brain injury (TBI) (median: 59.93 pg/mL), metabolic/toxic encephalopathy (median: 28.41 pg/mL), and hemorrhagic stroke (median: 24.09 pg/mL).
• Independent predictors of IL-6 levels include disease category, age (U-shaped association), and male sex.
• IL-6 demonstrated good diagnostic performance for distinguishing TBI, metabolic/toxic encephalopathy, and hemorrhagic stroke from healthy status.
• Limited discriminatory power for differential diagnosis between TBI and other neurological diseases.

Interpretation:

Serum IL-6 is a promising neuroinflammatory biomarker for acute brain injury screening, requiring age- and sex-stratified reference intervals for clinical interpretation.

Limitations:

• Study is retrospective and non-interventional, which may introduce biases.
• Diagnostic utility in emergency triage settings needs further validation.
• Prospective validation required for the proposed clinical interpretation framework.

Conclusion:

Serum IL-6 levels can serve as a preliminary screening indicator for acute neurological conditions, warranting further research in multi-center cohorts.