CSF
lactate measurement is recommended when nosocomial
meningitis is suspected, but its value in community-acquired
bacterial meningitis is controversial. We evaluated the diagnostic performance of
lactate and other CSF parameters in a prospective cohort of adult patients with acute
meningitis. Diagnostic accuracy of
lactate and other CSF parameters in patients with microbiologically documented episodes was assessed by receiver operating characteristic (ROC) curves. The cut-offs with the best diagnostic performance were determined. Forty-five of 61 patients (74%) had a documented bacterial (n = 18; S. pneumoniae, 11; N. meningitidis, 5; other, 2) or viral (n = 27 enterovirus, 21; VZV, 3; other, 3) etiology. CSF parameters were significantly different in bacterial vs.
viral meningitis, respectively (p < 0.001 for all comparisons): white cell count (median 1333 vs. 143/mm(3)),
proteins (median 4115 vs. 829 mg/l), CSF/
blood glucose ratio (median 0.1 vs. 0.52),
lactate (median 13 vs. 2.3 mmol/l). ROC curve analysis showed that CSF
lactate had the highest accuracy for discriminating bacterial from
viral meningitis, with a cutoff set at 3.5 mmol/l providing 100% sensitivity, specificity, PPV, NPV, and efficiency. CSF
lactate had the best accuracy for discriminating bacterial from
viral meningitis and should be included in the initial diagnostic workup of this condition.