A 6-year-old child presents with fever, severe headache, and nuchal rigidity. CSF analysis shows: protein 120 mg/dL, glucose 35 mg/dL (serum glucose 90 mg/dL), WBC 800 cells/mm³ with 90% neutrophils. CSF Gram stain shows Gram-negative diplococci. Which of the following CSF findings would most strongly support a bacterial etiology over viral meningitis?
- A CSF:serum glucose ratio below 0.6
- B CSF:serum glucose ratio below 0.4 combined with CSF WBC above 1000 with predominant neutrophilia ✓
- C CSF protein above 45 mg/dL
- D CSF opening pressure above 20 cm H2O
Explanation
While any CSF glucose ratio below 0.6 or protein above 45 mg/dL can occur in bacterial or viral meningitis, the combination of CSF:serum glucose ratio below 0.4 (reflecting robust bacterial sugar consumption), WBC above 1000/mm³ with predominant neutrophilia (>80%), and elevated protein (>100 mg/dL) is most specific for bacterial meningitis. Viral meningitis typically shows lymphocytic pleocytosis with normal or mildly reduced glucose. A CSF:serum glucose ratio below 0.4 has good specificity for bacterial meningitis and is a key threshold used in clinical scoring systems like the Bacterial Meningitis Score.
Reference: Ghai Essential Pediatrics, 10th ed.
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Written and medically reviewed by the StethoPrep medical team.