The role of cerebrospinal fluid (CSF)
lactate in
tuberculosis meningitis (TBM) diagnosis and prognosis is unclear. The aim of this study was to evaluate the performance of CSF
lactate alone and in combination with CSF
glucose in predicting a diagnosis of TBM and 14-day survival. HIV-positive Ugandan adults were investigated for suspected
meningitis. The baseline CSF tests included smear microscopy; Gram
stain; cell count;
protein; and point-of-care
glucose,
lactate, and cryptococcal
antigen (CrAg) assays. Where CrAg was negative or there was suspicion of TBM, a CSF Xpert MTB/RIF Ultra (Xpert Ultra) test was performed. We recorded baseline demographic and clinical data and 2-week outcomes. Of 667 patients, 25% (n = 166) had TBM, and of these, 49 had definite, 47 probable, and 70 possible TBM. CSF
lactate was higher in patients with definite TBM (8.0 mmol/L; interquartile ratio [IQR], 6.1 to 9.8 mmol/L) than in those with probable TBM (3.4 [IQR, 2.5 to 7.0] mmol/L), possible TBM (2.6 [IQR 2.1 to 3.8] mmol/L), and non-TBM disease (3.5 [IQR 2.5 to 5.0] mmol/L). A 2-fold increase in CSF
lactate was associated with 8-fold increased odds of definite TBM (odds ratio, 8.3; 95% confidence interval [CI], 3.6 to 19.1; P < 0.01) and 2-fold increased odds of definite/probable TBM (odds ratio, 2.3; 95% CI, 1.4 to 3.7; P < 0.001). At a cut point of >5.5 mmol/L, CSF
lactate could be used to diagnose definite TBM with a sensitivity of 87.7%, specificity of 80.7%, and a negative predictive value of 98.8%. CSF
lactate was not predictive of 2-week mortality. IMPORTANCE
Tuberculosis meningitis (TBM) is the most severe form of
tuberculosis, and its fatality is largely due to delays in diagnosis. The role of CSF
lactate has not been evaluated in patients with HIV presenting with signs and symptoms of
meningitis. In this study, using a point-of-care handheld
lactate machine in patients with HIV-associated
meningitis, we showed that high baseline CSF
lactate (>5.5 mmol) may be used to rapidly identify patients with TBM and shorten the time to initiate treatment with a similar performance to the Xpert Ultra assay for definite TBM. Elevated CSF
lactate levels, however, were not associated with increased 2-week mortality in patients with HIV-associated TBM. Due to moderate specificity, other etiologies of
meningitis should be investigated.