DOI: 10.1097/CCM.0b013e318223b939
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PMID: 21926508
Issn Print: 0090-3493
Publication Date: 2011/10/01
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Excerpt
Heparin-binding protein, as well as other cerebrospinal fluid (CSF) diagnostic markers, has been used to rapidly differentiate ABM from viral/aseptic meningitis (VAM). At our institution over the past 20 yrs, CSF lactic acid levels have been included in CSF profiles for possible meningitis (2, 3). Our CSF lactic acid break points are <3 mmol/L for VAM, 3–6 mmol/L for partially treated bacterial meningitis (PTBM), and >6 mmol/L for ABM. CSF lactic acid levels have the advantages of accurate breakpoints, rapidity, low cost, and can be done without special equipment. CSF lactic acid levels depend on timely specimen processing and numbers of red blood cells (RBCs) (2). CSF RBCs increase lactic acid levels proportional to number of CSF RBCs (2, 3). Their data did not include CSF RBC counts. Delay in CSF processing/RBCs may explain why some VAM/PTBM patients in their study had CSF lactic acid levels of 3–6 mmol/L (1).
CSF lactic acid levels are also helpful in some types of chronic meningitis, e.g., CSF lactic acid levels are increased in tuberculous and fungal meningitis but not in sarcoid meningitis or meningeal carcinomatosis (2). Since herpes simplex virus and Listeria meningitis/encephalitis, CSF RBCs, often present a difficult diagnostic problem. CSF lactic acid levels are particularly helpful in this setting since CSF lactic levels are elevated with Listeria but not herpes simplex virus meningitis/encephalitis (2, 3).
In patients with possible meningitis, normal CSF lactic acid levels of ≤3.0 mm/L, and negative CSF Gram stains, we have not had to treat empirically with antibiotic and have not had to treat presumptively with antibiotic therapy. CSF lactic acid levels have saved our hospital tens of thousands of dollars by avoiding needless empirical antibiotic therapy for VAM while awaiting CSF cultures to be reported negative. In patients with PTBM, CSF Gram stains/cultures are also negative. We treat patients with PTBM and CSF lactic levels of 4–6 mm/L for ABM. Since 64% of their patients received prior antibiotics, undoubtedly some were PTBM cases as indicated by the range of their CSF lactic acid levels (1). CSF lactic acid levels readily differentiate ABM from VAM and PTBM.
Heparin-binding protein is another CSF diagnostic marker that appears to be useful in differentiating ABM from VAM. However, in my view as well as that of others, CSF lactic acid levels remain the most accurate/rapid CSF test to differentiate ABM from VAM and PTBM (4, 5). In our hospital, CSF lactic acid levels have been critical in guiding therapeutic decisions (2, 3). In most hospitals, empirical antimicrobial therapy for possible ABM is often given for 3–5 days until culture results are reported. However, in patients with possible ABM, antibiotic therapy is unnecessary if CSF lactic acid levels are <3 mmol/L. Other hospitals may also benefit from considerable savings realized by avoiding unnecessary antimicrobial therapy for possible ABM based on CSF lactic acid levels.
The author has not disclosed any potential conflicts of interest.
