![]() ![]() For a positive test (blue line): ( a) CSF lactate (>3.65 mol/L). Prior probability (odds) of acute BM: 45%. LR, likelihood ratio.įagan’s nomogram was used to calculate posterior probability for lactate, GL, WBC in CSF, and their associations for positive and negative tests in the groups with definite acute meningitis and with atypical acute BM. The red line indicates the posterior odd for a negative test. Predominance of neutrophils in CSF, posterior probability (odds) was 47% (95% CI 31–64%). CSF/blood GL ratio (<0.6), posterior probability (odds) was 55% (95% CI 49–61%). Approximately 1 in 1.1 with positive test had acute BM. ![]() Resultsįagan’s nomogram was used to calculate posterior probability for lactate, GL, WBC in CSF, and their associations for positive and negative tests in the groups with definite acute meningitis and with atypical acute BM. FP rate (%) = 100 – positive predictive value presumptive positive = (TP + FP)/total detection rate = TP/total error ratio = (FP + FN)/TP and combined error = (FP + FN)/total. The posttest probability for a positive and negative test was calculated using the Fagan’s nomogram, considering the pretest probability of acute BM to be 45%. The positive and negative likelihood ratios (LR+ and LR–, respectively) were calculated. CUI was classified as follows: utility excellent, ≥0.81 good, ≥0.64 fair, ≥0.49 poor, ≤0.49 and very poor, ≤0.36. The following performance characteristics were calculated: sensitivity, specificity, accuracy (efficiency), positive predictive value, negative predictive value, Youden’s index (J) = ( – 1), error ratio = (false positive + false negative )/true positive (TP), clinical utility index positive (CUI+), and CUI negative (CUI–, screening accuracy). The performance characteristics of the CSF biomarkers for acute meningitis were calculated using positive CSF culture for bacteria as the reference method. To study the accuracy of the CSF biomarkers in diagnosing atypical acute BM, this group was further subdivided into (a) definitive acute BM with typical CSF cell characteristics, that is, increase in total WBC with predominance of neutrophils ( n = 43 76.8%), and (b) definitive acute BM with atypical CSF cell characteristics, that is, increase in total WBC with predominance of lymphocytes or normal CSF WBC count (≤5 × 10 6/L, n = 13, 23.2%). Thirty-four cases (54%) were due to gram-positive bacteria: Streptococcus pneumoniae ( n = 18), coagulase-negative staphylococci ( n = 9), Staphylococcus aureus ( n = 4), Group D Streptococcus ( n = 1), Streptococcus viridans ( n = 1), and Streptococcus sanguinis ( n = 1) 29 cases (46%) were gram-negative bacteria: Neisseria meningitidis ( n = 9), Enterobacter cloacae ( n = 6), Klebsiella pneumoniae ( n = 5), Acinetobacter ( n = 2), Escherichia coli ( n = 2), Haemophilus influenzae ( n = 1), Enterobacter aerogenes ( n = 1), Klebsiella oxytoca ( n = 1), Proteus mirabilis ( n = 2), and Pseudomonas stutzeri ( n = 1). Group 1, definitive acute BM ( n = 63): all cases were caused by bacteria identified by culture. Conclusion: The CSF lactate assay can be routinely used in laboratories as a rapid, automated, and easy method that is independent of lactate blood levels. ![]() CSF lactate showed better operational characteristics than those of CSF GL and CSF/blood GL ratio, presenting the highest positive likelihood ratio, and thus aided in the differential diagnosis of VM with atypical CSF. Definitive acute BM or VM with atypical CSF cell characteristics was observed in 23.2 and 21.6% of samples, respectively, and these groups showed reduced performance of characteristics of all CSF biomarkers. CSF lactate presented higher specificity (92%) and negative predictive value (94%) compared to CSF GL and CSF/blood GL ratio in distinguishing acute BM and VM. Results: Lactate level in the CSF of acute BM group was 4-fold higher than that in the acute VM and control groups ( p < 0.0001). Methods: Three hundred and twenty-four CSF reports were included, which were distributed as the acute BM, VM, and normal control groups ( n = 63, 139, and 122, respectively). We compared the ability of lactate and glucose (GL) in CSF and the CSF/blood GL ratio to distinguish between acute BM and VM with typical and atypical CSF characteristics. Objective: Several cerebrospinal fluid (CSF) biomarkers are used to distinguish between acute bacterial meningitis (BM) and viral meningitis (VM). ![]()
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