Cerebrospinal Fluid Lactate in Tubercular Meningitis: Diagnostic or Prognostic Marker?

Diagnosis of tubercular meningitis (TBM) continues to be a clinical challenge and available microbiological tests fail to attain the required accuracy standards. As a result, most guidelines for the diagnosis and management of TBM depend on clinical setting, cerebrospinal fluid (CSF) analyses including adenosine deaminase activity (ADA), and imaging to guide decisionmaking. Delay in diagnosis leads to high mortality and morbidity. As there is scarcity of data on CSF lactate in TBM and its role as a diagnostic and prognostic marker, study of CSF Lactate in TBM Patients was undertaken.In this hospital based cross sectional study all admitted patients of meningo-encephalitis aged more than 15 years who fulfilled the diagnostic criteria for TBM were included. Routine haematological and biochemical investigations were done in all the patients. The CSF analysis was done including all routine microscopic parameters, lactate, Gram's stain, AFB and culture. Patients included were classified as definite, probable, or possible TBM as per WHO diagnostic criteria and were classified into three clinical stages using criteria laid down by the British Medical Research Council.Fifty five patients fulfilling the diagnostic criteria for tubercular meningitis were studied. Most of the patients were in stage II according to severity. An increase in CSF lactate and CSF ADA levels with increase in severity of clinical stage of TBM was observed. Other CSF parameters and imaging were not significantly different in various groups.CSF lactate levels of study patients were higher than normal and showed increasing trend from possible to definite diagnosis of TBM suggesting that CSF lactate could be a predictor of definite diagnostic class of TBM though more studies with large number of patients are needed to prove its utility as prognostic tool.