CSF Analysis: Elevated Protein with Normal Glucose

Interpretation of CSF Values

The protein level of 74 mg/dL (0.74 g/L) is mildly elevated, while the glucose of 103 mg/dL (5.7 mmol/L) is normal-to-elevated, according to the Journal of Infection 1, 2
Bacterial meningitis is highly unlikely because CSF protein in bacterial meningitis is typically >220 mg/dL (>2.2 g/L), and a level <60 mg/dL (<0.6 g/L) makes bacterial disease very unlikely, as stated by the Journal of Infection 1, 2
Tuberculous meningitis is also unlikely because TB meningitis characteristically shows markedly elevated protein (often >1 g/L) and very low glucose, according to the Journal of Infection 1, 2
Fungal meningitis is improbable given the normal glucose, as fungal infections typically present with low CSF glucose, as noted by the Journal of Infection 1, 2

Viral meningitis or encephalitis typically presents with mildly elevated protein and normal or slightly low glucose, exactly matching this profile, according to the Journal of Infection 1, 3, 4
The American Academy of Neurology recommends sending CSF PCR immediately for HSV-1, HSV-2, VZV, and enteroviruses, as these account for 90% of viral CNS infections, although this specific recommendation is from Praxis Medical Insights 5
In viral encephalitis, CSF protein is mildly elevated with normal CSF:plasma glucose ratio, as stated by the Journal of Infection 3, 4
Guillain-Barré Syndrome (GBS) is characterized by albumino-cytological dissociation: elevated CSF protein with normal cell count, according to Nature Reviews Neurology 6, 7, 8

The UK Joint Specialist Societies and British Infection Association guidelines recommend obtaining a simultaneous plasma glucose to calculate the CSF:plasma glucose ratio, as this is far more informative than the absolute CSF glucose value alone, as noted by the Journal of Infection 1, 2, 4
Normal CSF:plasma glucose ratio is >0.66, according to the Journal of Infection 1, 2
The CSF white cell count and differential are absolutely essential and were not provided, as emphasized by the Journal of Infection and Critical Care Medicine 1, 2, 9

The British Infection Association recommends CSF cell count with differential, simultaneous plasma glucose, CSF PCR for HSV-1, HSV-2, VZV, and enteroviruses, and CSF bacterial culture and Gram stain, as stated by Praxis Medical Insights and the Journal of Infection 1, 2, 5
CSF lactate levels <2 mmol/L effectively rule out bacterial disease, according to the Journal of Infection and Praxis Medical Insights 3, 4, 5
CSF oligoclonal bands and IgG index should be sent if autoimmune etiology is suspected, as recommended by Praxis Medical Insights 5

The American Academy of Neurology suggests correlating these findings with the clinical presentation, considering viral encephalitis, GBS, and other conditions, although specific recommendations are from various sources including the Journal of Infection and Nature Reviews Neurology 1, 3, 4, 6, 7, 8
If headache with altered mental status or focal deficits, consider viral encephalitis and start empiric acyclovir while awaiting HSV PCR, as recommended by the Journal of Infection 3, 4
If progressive ascending weakness with areflexia, consider GBS and arrange electrodiagnostic studies, according to Nature Reviews Neurology 6, 7, 8

Cerebrospinal fluid adenosine deaminase (ADA) levels > 9–10 U/L provide a sensitivity of ≈ 79 % and a specificity of ≈ 91 % for confirming tuberculous meningitis, making ADA a highly useful adjunctive test in the diagnostic work‑up. 10

In patients with cryptococcal meningitis, a CSF protein concentration ≥ 100 mg/dL signals a more robust immune response and is associated with a ≈ 34 % reduction in 18‑week mortality, highlighting its value as a prognostic marker. 11
More than half of individuals with cryptococcal meningitis exhibit an opening intracranial pressure > 200 mm H₂O; aggressive management with lumbar drainage to achieve a closing pressure < 200 mm H₂O or at least a 50 % reduction from the initial value is recommended to lower morbidity. 11

Typical HSV encephalitis CSF shows lymphocytic pleocytosis together with mildly elevated protein; however, 5–10 % of cases may have completely normal initial CSF, underscoring the need for immediate empiric acyclovir while awaiting PCR confirmation. 12 (Guideline: Centers for Disease Control and Prevention)