What is the role of CSF glucose concentration in the workup of Haemophilus influenzae type b (Hib) meningitis?

Updated: Jul 09, 2018
  • Author: Prateek Lohia, MD, MHA; Chief Editor: Niranjan N Singh, MBBS, MD, DM, FAHS, FAANEM  more...
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Answer

CSF glucose concentrations lower than 40 mg/dL are found in approximately two thirds of all cases of acute bacterial meningitis. Comparison must always be made to serum glucose concentrations measured at the time of the lumbar puncture. The CSF-to-serum-glucose ratios should be approximately 2:3 (ie, 0.6).

In the presence of an elevated serum glucose concentration, a CSF glucose concentration within the reference range may not actually be normal, because the CSF value must be interpreted with respect to the serum value. A CSF-to-serum-glucose ratio of less than 0.31 is observed in 70% of patients with bacterial meningitis. Low CSF-to-serum glucose ratios are also found in fungal and carcinomatous meningitides.

In as many as 80% of patients who receive appropriate IV antibiotic treatment for bacterial meningitis, CSF glucose concentration returns to the reference range by day 3 of that treatment. Even with appropriate treatment, however, some patients continue to exhibit low CSF glucose concentrations for 7-10 days.


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