What is the interpretation of a spinal fluid report with mild hyperproteinemia, elevated WBC count, and normal glucose level in a patient with a likely neurological condition?

CSF Analysis Interpretation: Aseptic Meningitis Pattern

This CSF profile shows a classic aseptic (viral or autoimmune) meningitis pattern with lymphocytic pleocytosis, mildly elevated protein, and preserved glucose—requiring immediate exclusion of tuberculous meningitis, partially treated bacterial meningitis, and fungal infections before considering viral or autoimmune etiologies. 1

Key CSF Findings Analysis

Your CSF demonstrates:

• WBC 8 cells/μL with 100% lymphocytes: Mild lymphocytic pleocytosis (normal <5/μL) 2
• Protein 43 mg/dL: Mildly elevated (normal 15-45 mg/dL) 2
• Glucose 51 mg/dL: Normal to borderline low—critical to calculate CSF/plasma glucose ratio immediately 1
• Clear, colorless appearance with 0 RBCs: Rules out traumatic tap and subarachnoid hemorrhage 2

Critical Immediate Actions

Calculate CSF/Plasma Glucose Ratio NOW

• If ratio <0.5: Tuberculous meningitis is highly likely 1
• If ratio <0.36: Bacterial meningitis becomes more probable 1
• If ratio >0.66: Normal, supports viral or autoimmune etiology 1
• The absolute CSF glucose of 51 mg/dL can be misleading without knowing serum glucose 1

Mandatory Additional CSF Studies Before Treatment

• Mycobacterial testing: AFB smear, TB culture, and TB PCR on 6 mL CSF 1
• Bacterial studies: Gram stain, bacterial culture, CSF lactate (if <2 mmol/L, effectively rules out bacterial disease) 1
• Viral PCR panel: HSV, VZV, enterovirus at minimum 3
• Fungal studies: Cryptococcal antigen, fungal culture (especially if immunocompromised) 1
• CSF cytology: To exclude leptomeningeal metastases 1, 4
• Opening pressure: Should have been measured during LP 1

Differential Diagnosis Priority

1. Tuberculous Meningitis (MUST EXCLUDE FIRST)

• Lymphocytic predominance is characteristic, though neutrophils may dominate early 1
• Protein typically >100 mg/dL (yours is only 43 mg/dL, making TB less likely but not excluded) 1
• Subacute course >5 days has 93% sensitivity for TB meningitis 1
• Start empiric four-drug anti-TB therapy immediately if clinical suspicion exists, without waiting for confirmation 1

2. Partially Treated Bacterial Meningitis

• Can present with lymphocytic pleocytosis after antibiotic exposure 1
• Bacterial meningitis typically shows neutrophil predominance (80-95%), but early treatment changes this 1
• CSF lactate <2 mmol/L effectively excludes bacterial disease 1

3. Viral (Aseptic) Meningitis

• Most likely if CSF/plasma glucose ratio is normal (>0.66) 3
• Moderate pleocytosis with lymphocytic predominance fits this pattern 3
• Mildly elevated protein and normal glucose are typical 3
• Start IV acyclovir 500 mg/m² every 8 hours immediately until HSV is excluded 1

4. Autoimmune/Immune-Related Meningitis

• Seen with immune checkpoint inhibitors or autoimmune conditions 3
• Elevated WBC with normal glucose, normal culture, and Gram stain 3
• May see reactive lymphocytes or histiocytes on cytology 3

5. Fungal Meningitis (Cryptococcal, Histoplasma)

• Similar CSF profile: lymphocytic pleocytosis, low glucose, raised protein 1
• More common in immunocompromised patients 1
• Requires specific antigen testing and fungal cultures 1

Treatment Algorithm

Immediate Empiric Therapy (Start Before Results Return)

1. IV acyclovir 500 mg/m² every 8 hours until HSV excluded 1
2. If any concern for bacterial infection: Add empiric antibiotics (vancomycin + ceftriaxone) until bacterial studies negative 3, 1
3. If TB meningitis suspected clinically: Start four-drug anti-TB therapy (isoniazid, rifampin, pyrazinamide, ethambutol) immediately 1

Adjust Based on CSF/Plasma Glucose Ratio

• Ratio <0.5: Treat as TB meningitis empirically 1
• Ratio 0.5-0.66: Continue broad coverage, await cultures 1
• Ratio >0.66: Viral etiology most likely, continue acyclovir until PCR results 1

Critical Pitfalls to Avoid

• Never delay antimicrobial therapy while waiting for CSF results if infection is suspected 3, 1
• Do not assume viral meningitis without excluding TB, partially treated bacterial, and fungal causes 1
• Single negative CSF cytology does not exclude leptomeningeal disease—repeat if clinical suspicion persists 4
• Reactive CSF pleocytosis after repeat LP is rare (0.96%), so elevated WBC should prompt thorough infectious workup 5
• Early bacterial or viral meningitis may show atypical cell differentials—neutrophils can dominate viral early, lymphocytes can appear in bacterial after treatment 2

Follow-Up Strategy

• Repeat LP in 24-48 hours if diagnosis remains unclear or patient deteriorates 3
• Monitor clinical response to empiric therapy closely 1
• Adjust treatment based on culture results, PCR, and clinical trajectory 1
• If all infectious workup negative and autoimmune suspected, consider MRI brain with contrast and autoimmune encephalopathy panel 3