Cerebrospinal fluid lactic acid dehydrogenase activity. Levels in untreated and partially antibiotic-treated meningitis.

High levels of cerebrospinal fluid (CSF) lactic acid dehydrogenase (LDH) activity were found in 23 cases of bacterial meningitis, but significantly lower levels of CSF LDH activity were observed in 11 patients with viral meningitis and in 13 patients with no central nervous system infection. No correlation was found between levels of CSF LDH activity and specific agents or the amounts of CSF white blood cell, protein, and glucose. The number of meningitis cases of unknown cause that could be classified as probably bacterial or viral was increased by determination of the level of CSF LDH activity. The level of CSH LDH activity is useful in differentiating bacterial from viral meningitis and, along with determination of the CSF blood cell counts and protein and glucose levels, aids in classification of meningitis before culture results are available.