Value of Cerebrospinal Fluid Lactate for the Diagnosis of Bacterial Meningitis in Postoperative Neurosurgical Patients

Objective: To evaluate the diagnostic value of CSF lactate (L(CSF)) for the diagnosis of bacterial meningitis (BM) following neurosurgery, and compare it with other CSF markers.

Methods: Prospective study of consecutive neurosurgical postoperative patients admitted to the Intensive Care Unit (ICU) at Maciel Hospital. Patients with clinical suspicion of BM were categorised, according to preset criteria, into 3 groups: (1) proven BM; (2) probable BM, and (3) excluded BM. CSF markers were plotted in a receiver operating curve (ROC) to evaluate their diagnostic accuracy.

Results: The study included 158 patients. We obtained 46 CSF samples from patients with clinical suspicion of BM by lumbar puncture (LP): 10 corresponded to proven BM, 4 to probable BM and 32 to excluded BM. Mean lactate in CSF (L(CSF)) was: 10.72±4.68mM for proven BM, 6.07±0.66mM for probable BM and 3.06±1.11mM for excluded BM (P<.001 for proven BM and probable BM vs excluded BM; P=NS for proven BM vs probable BM). L(CSF) displayed a better diagnostic accuracy for BM in the 2 scenarios studied: (1) positive bacterial CSF culture or Gram stain as positive control (gold standard) (sensitivity: 87%, specificity: 94%, cut-off value: 5.9mM), and (2) combination of proven BM and probable BM as positive control (sensitivity: 92%, specificity: 100%, cut-off value: 5.2mM).

Conclusions: According to our results, determination of L(CSF) is a quick, sensitive and specific test to identify the need for antimicrobial therapy in neurosurgical postoperative patients with clinical suspicion of BM.