BackgroundCerebrospinal fluid (CSF) analysis is a sensitive tool for evaluating patients with neurologic diseases but is rarely specific. Biomarkers can be measured from any bodily fluid and can be useful indicators for the presence, severity, and prognosis of diseases.ObjectivesThis study was designed to evaluate if CSF lactate can be used as a biomarker in dogs with central nervous system disease.MethodsPeripheral venous blood and CSF were collected from 49 dogs with various intracranial diseases to evaluate correlations between blood and CSF lactate levels. Total nucleated cell count (TNCC) and CSF protein concentrations were also evaluated. All samples obtained were divided into normal (NG) and abnormal (AG) dogs based on a TNCC of ≤5 and >5 cells/μL and a protein concentration of ≤25 and >25 mg/dL, respectively. The AG dogs were further subdivided into those having <100 TNCCs/µL (AGL) and those having >100 TNCCs/µL (AGH). They were also subdivided into groups based on seizure activity (AGS), and inflammatory (AGI), or neoplastic diseases (AGN), and the respective lactate concentrations were then compared.ResultsLactate concentrations were significantly increased in CSF and venous blood samples in the AG compared with the NG dogs, but no differences were found among the individual disease processes. In all dogs, CSF lactate concentrations were higher than venous blood lactate levels; however, no direct correlation between CSF and blood lactate concentrations was identified.ConclusionsCerebrospinal fluid lactate can be used as a biomarker in clinical settings as it can be measured via a commercially available lactometer immediately after collection without the need for special instrumentation or laboratory personnel.