Biochemical characterization of cerebrospinal fluid in leptomeningeal carcinomatosis and infectious meningitis using the metabolic product model: a diagnostic performance evaluation in a single-center retrospective cohort

BACKGROUND: Leptomeningeal metastasis (LM) and infectious meningitis often present with similar neurological symptoms, making clinical differentiation challenging. We retrospectively analyzed cerebrospinal fluid (CSF) biochemistry (lactate (LAC), lactate dehydrogenase (LDH), protein, glucose) in patients with confirmed LM and infectious meningitis (bacterial or viral) to delineate characteristic metabolic profiles. RESEARCH DESIGN AND METHODS: In this single-center retrospective cohort, we included 39 patients with cytology-confirmed LM, 38 with bacterial meningitis (BM), and 40 with viral meningitis (VM). We calculated an LDH × LAC product and compared its diagnostic performance to traditional biochemical markers using ROC analysis and DeLong tests for area under the curve differences. RESULTS: /L) and 66.7% had ≤20% tumor cells, yet LDH×LAC remained highly sensitive even in these low-burden cases. CONCLUSIONS: These findings highlight that certain biochemical signatures can distinguish etiologies whereby high CSF lactate favors bacterial infection or aggressive tumor involvement, whereas normal glucose and low lactate favor viral causes. Our results emphasize distinct CSF signatures in neoplastic compared to infectious meningitis, suggesting metabolic profiling can aid diagnosis.