From the Guidelines
Clinical Distinction between Viral and Bacterial Meningitis is Crucial Bacterial meningitis requires prompt initiation of antimicrobial therapy, whereas viral meningitis is typically managed supportively.
Key Distinctions
- CSF Glucose: Bacterial meningitis tends to have lower CSF glucose levels, with a CSF:plasma glucose ratio of less than 0.36 being highly sensitive and specific for bacterial meningitis 1.
- CSF Protein: Bacterial meningitis tends to have higher CSF protein levels, with a level of less than 0.6 g/L making bacterial disease unlikely 1.
- CSF Lactate: A CSF lactate level of greater than 35 mg/dl is highly sensitive and specific for bacterial meningitis, but only if antibiotics have not been given beforehand 1.
- White Blood Cell Count: Bacterial meningitis typically presents with a neutrophil predominance, whereas viral meningitis presents with a lymphocytic predominance 1.
- Gram Stain: A positive Gram stain is highly specific for bacterial meningitis, but may not be sensitive enough to rule out the disease 1.
Important Considerations
- Timing of Antibiotics: Administration of antibiotics prior to lumbar puncture can affect CSF results, particularly lactate levels 1.
- Interpretation of CSF Results: CSF results must be interpreted in the context of the clinical presentation, as no single parameter can provide an absolute indication of the cause of meningitis 1.
- Empiric Treatment: Empiric treatment with antimicrobial therapy, such as ceftriaxone or cefotaxime, may be considered in suspected bacterial meningitis, and dexamethasone may be used in certain cases 1.
From the Research
Clinical Distinctions between Viral and Bacterial Meningitis
The clinical distinctions between viral and bacterial meningitis can be identified through various laboratory tests and biomarkers. Some of the key distinctions include:
- Higher levels of procalcitonin (PCT), C-reactive protein (CRP), and lactate in bacterial meningitis patients compared to viral meningitis patients 2, 3, 4
- Higher peripheral and CSF-leukocytosis, higher CSF-protein, and lower CSF-glucose levels in bacterial meningitis patients compared to viral meningitis patients 2
- The presence of certain microorganisms, such as Neisseria meningitides and varicella-zoster virus, which are commonly associated with bacterial and viral meningitis, respectively 2
- The use of biomarkers, such as ferritin, which has been shown to be elevated in bacterial meningitis patients compared to viral meningitis patients 5
Biomarkers for Differentiation
Several biomarkers have been identified as potential markers for differentiating between bacterial and viral meningitis, including:
- Procalcitonin (PCT) 2, 6
- C-reactive protein (CRP) 3, 4, 6
- Lactate 3
- Ferritin 5
- CSF-protein and CSF-glucose levels 2, 3
Diagnostic Accuracy
The diagnostic accuracy of these biomarkers varies, but some have been shown to have high sensitivity and specificity for distinguishing between bacterial and viral meningitis. For example:
- Serum PCT and CSF-protein have been shown to have an area under the curve (AUC) of 0.998, with 100% sensitivity and 97.1% specificity for predicting bacterial meningitis 2
- CSF lactate has been shown to have an AUC of 0.97, with 94.12% sensitivity and 100% specificity for predicting bacterial meningitis 3
- Serum CRP has been shown to have high sensitivity (96%) and specificity (93%) for distinguishing between Gram stain-negative bacterial meningitis and viral meningitis 4