What are the cerebrospinal fluid (CSF) characteristics in acute bacterial meningitis?

Updated: Jul 16, 2019
  • Author: Rodrigo Hasbun, MD, MPH; Chief Editor: Michael Stuart Bronze, MD  more...
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Examination of the CSF in patients with acute bacterial meningitis reveals the characteristic neutrophilic pleocytosis (cell count usually ranging from hundreds to a few thousand, with >80% PMNs). In some (25-30%) cases of L monocytogenes meningitis, a lymphocytic predominance may occur. A low CSF white blood cell (WBC) count (< 20/µL) in the presence of a high bacterial load suggests a poor prognosis.

According to Seupaul, the following 3 findings on CSF analysis have clinically useful likelihood ratios for the diagnosis of bacterial meningitis in adults [28] :

  • CSF glucose−to−blood glucose ratio of 0.4 or lower

  • CSF WBC count of 500/µL or higher

  • CSF lactate level of 31.53 mg/dL or higher

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