Cerebrospinal fluid lactate and lactate dehydrogenase levels as diagnostic aids in tuberculous meningitis

The value of cerebrospinal fluid (CSF) lactate and lactate dehydrogenase (LD) values as aids in differentiating tuberculous meningitis (TBM) from aseptic meningitis has been investigated. Using an upper limit of normal for CSF lactate levels of 2,75 mmol/l resulted in detection of 24 out of 26 cases of TBM (a sensitivity of 92%). If, however, a level of 3,85 mmol/l was taken as the upper limit of normal, then 18 out of 26 cases were detected (a sensitivity of 69%). Using 40 U/l as the upper limit of normal for LD levels detected 21 out of 38 cases of TBM (a sensitivity of 55%). Both tests may give normal values in the presence of TBM, but this should not cause specific antituberculosis therapy to be withheld. Neither test appears to hold marked advantages over conventional chemical analysis of CSF in differentiating TBM from aseptic meningitis.