[Assay of lactic acid in the cerebrospinal fluid for the diagnosis of bacterial meningitis. Strategies for the choice of discriminatory threshold].

OBJECTIVES

In search for a supplementary marker of bacterial meningitis in cases where conventional bacteriology, cytology and chemistry are insufficiently contributive to diagnosis, we assessed the value of cerebrospinal fluid lactate levels in children with bacterial meningitis.

PATIENTS AND

METHODS

Cerebrospinal fluid lactate levels were measured from all spinal taps performed in a pediatric emergency care unit over a two-year period. Of the 332 usable samples there were 32 cases of bacterial meningitis, 104 cases of viral meningitis and 196 other diagnoses (non meningitis).

RESULTS

Average lactate concentration 7 +/- 4 mmol/l in bacterial meningitis versus 2.1 +/- 0.6 mmol/l in viral meningitis (p < 0.0001). The value of lactic acid concentrations in discriminating between bacterial and viral meningitis was found to be superior to that of other chemistry results: protein, glucose, chloride. The discriminatory threshold of cerebrospinal fluid lactate was 3.7 mmol/l with sensitivity of 80% and a specificity of 98%.

CONCLUSION

We propose routine assay of cerebrospinal fluid lactate in all cases of suspected meningitis.