A comprehensive investigation into the ranges of laboratory tests present in cerebrospinal fluid across various types of meningitis within different age categories

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Background. Diagnosing meningitis requires a lumbar puncture to analyze cerebrospinal fluid (CSF) and determine the causative pathogen. Key diagnostic measures include Glucose and Protein concentrations, cell count, differential leukocyte count, Gram stain, culture, and PCR if necessary. Objective. Our analysis assessed patterns in key biomarkers—neutrophils, lymphocytes, cerebrospinal fluid white blood cell count, and CSF/blood Glucose and Protein ratios—across various types of meningitis, including meningococcemia, meningococcal, tuberculous, pneumococcal, aseptic, and other bacterial meningitis. We examined these biomarkers within distinct age categories: children (0-12 years), adults (13-64 years), and the elderly (≥ 65 years). Methods. Descriptive statistics were used to analyze various types of meningitis across different age groups. We assessed the normality of laboratory biomarkers using the Shapiro-Wilk test, and applied Welch ANOVA to explore potential differences in biomarker levels among various types of meningitis. A Games-Howell post hoc test was used to identify specific pairs of meningitis types with statistically significant differences in biomarker levels. Results. The analysis of variance of cerebrospinal fluid biomarkers revealed significant differences in CSF WCC (cells/mm3), Neutrophils (%), Lymphocytes (%), CSF/blood Glucose and Protein ratios in children and adults (p <0.05). However, differences were observed solely in neutrophil levels among elderly subjects. In bacterial meningitis, neutrophil levels increased across all ages, with adults showing higher levels. For meningococcal meningitis, adults had a median neutrophil level of 78.5% [60%, 90%] compared to 57% [24.5%, 85.25%] in children. The CSF white cell count (WCC) median was also higher in adults (339 cells/mm³) compared to children (224 cells/mm³). Viral meningitis cases exhibited higher lymphocyte levels across all age groups, with medians of 69% [34%, 87%] in children, 82% [61%, 93%] in adults, and 77% [55%, 90%] in the elderly. The glucose ratio was lower in bacterial meningitis (<0.3) and higher in viral cases (>0.5). Protein ratios were elevated in bacterial meningitis, indicating increased blood-brain barrier permeability. These results demonstrate a distinct biological profile for different causative agents, modulated by patient age.