Cerebrospinal fluid (CSF) lactate is produced by bacterial anaerobic metabolism and is not affected by blood lactate concentration, an advantage over CSF glucose in differentiating bacterial meningitis from aseptic meningitis. However, the previous investigations have shown mixed results of the sensitivity and specificity. Our study’s purpose was to assess the utility of CSF lactate in differentiating bacterial meningitis from aseptic meningitis.

We searched MEDLINE and EMBASE for clinical studies that included CSF lactate measurement in bacterial meningitis and aseptic meningitis. Test characteristics were pooled using hierarchical summary ROC curve and random effects model.

Thirty three studies were included. The pooled test characteristics of CSF lactate were sensitivity 0.93 (95% CI: 0.89–0.96), specificity 0.96 (95% CI: 0.93–0.98), likelihood ratio positive 22.9 (95% CI: 12.6–41.9), likelihood ratio negative 0.07 (95% CI: 0.05–0.12), and diagnostic odds ratio 313 (95% CI: 141–698). Pretreatment with antibiotics lowered the sensitivity 0.49 (95% CI: 0.23–0.75). CSF lactate of around 35 mg/dl (34–36 mg/dl) had higher sensitivity and specificity than those of around 27 mg/dl (26–28 mg/dl).

CSF lactate’s high negative likelihood ratio may make it useful for ruling out bacterial meningitis though pretreatment with antibiotics reduces clinical accuracy. CSF lactate of 35 mg/dl could be optimal cut-off value for distinguishing bacterial meningitis from aseptic meningitis.