Cerebrospinal Fluid Lactate as a Differential Biomarker for Bacterial and Viral Meningitis

Meningitis is a critical public health problem demanding immediate diagnosis and effective treatment due to high mortality rates. Cerebrospinal Fluid (CSF) lactate concentration is a promising test to distinguish bacterial from viral meningitis. This study aimed to assess the performance and usefulness of CSF lactate as a biomarker to differentiate between bacterial and viral meningitis, and to determine its optimal level to differentiate between them. This prospective study included 50 patients, presented to Abbassia Fever Hospital with clinical findings consistent with meningitis. Patients were divided into two groups: Group1 included 30 patients with bacterial meningitis. Group 2 included 20 patients with viral meningitis. CSF lactate and other conventional CSF parameters were recorded. For CSF culture, Streptococcus pneumoniae was identified in 53.3% of the bacterial meningitis group. The polymerase chain reaction (PCR) indicated that S. pneumoniae was present in 26/50 (52%) and 3/50 (6%) patients were PCR negative. Among bacterial meningitis patients, S. pneumoniae was the most pervasive organism 26/30 (86.7%). The mean CSF lactate level was 9.3 mmol/l ±5.0 (2.2-17.6). There was a statistically significant strong agreement (Kappa=0.957) between types of meningitis diagnosed by PCR, culture, and CSF lactate at cutoff level of 7.2 mmol/L. This cutoff value was the best to differentiate between bacterial and viral meningitis. The validity of CSF lactate as a differentiating tool showed sensitivity, specificity, positive predictive value, and negative predictive value of 93.3%, 100%, 100%, and 90.9%, respectively. In conclusion, CSF lactate could be a valuable, sensitive, specific, and rapid marker for identifying the most dangerous bacterial causes of CNS infection, especially S. pneumoniae. CSF lactate can be routinely used as an early biochemical warning marker and a useful point-of-care test. CSF lactate at cutoff level of >7.2 mmol/L can accurately detect S. pneumoniae, the most prevalent organism in Egypt.