How to read cerebrospinal fluid results
Other platforms explain it with text and video. In VMS you practice it on the patient.
A lumbar puncture helps diagnose meningitis, bleeding around the brain and other nerve diseases. A few numbers read together point to the likely cause.
Step by step
Do not delay antibiotics
In suspected bacterial meningitis, give antibiotics promptly. Do not wait for the lumbar puncture or CT. [1]
Check opening pressure and color
Normal fluid is clear. High pressure is common in bacterial, fungal and cryptococcal meningitis. [2]
Read the cell count
Mostly neutrophils suggests bacterial infection. Mostly lymphocytes suggests viral, fungal or tuberculosis infection. [2]
Compare CSF and blood glucose
CSF glucose is normally about 60% of blood glucose. A ratio under 0.4 suggests bacterial, fungal or tuberculosis infection. [2]
Check protein
Protein rises in infection, bleeding and some nerve diseases such as Guillain-Barre syndrome. [2]
Sort out red cells
Red cells that fall from tube 1 to tube 4 suggest a traumatic tap. Persistent red cells and yellow fluid (xanthochromia) suggest bleeding around the brain. [2]
Follow the stains and cultures
Check Gram stain, culture and PCR panels, and adjust antibiotics when results return. [1]
Common errors
- Delaying antibiotics while waiting for the lumbar puncture.
- Reading CSF glucose without a matching blood glucose.
- Calling a traumatic tap a brain bleed without comparing tubes.
Typical adult patterns; use your lab's ranges [2]
| Pattern | Cells | Glucose and protein |
|---|---|---|
| Normal | 0 to 5 white cells per microliter, lymphocytes | Glucose about 60% of blood; protein about 15 to 45 mg/dL |
| Bacterial | Hundreds to thousands, mostly neutrophils | Low glucose, high protein |
| Viral | Tens to hundreds, mostly lymphocytes | Normal glucose, normal or mildly high protein |
| Fungal or tuberculosis | Tens to hundreds, mostly lymphocytes | Low glucose, high protein |
Practice it in VMS
In VMS you do this on the patient, not on paper: every step goes on the checklist with a score, and in Teach mode Blocky tells you what comes next.
VMS cases that train this skill
Sources
Facts and steps follow AAMC Core Entrustable Professional Activities (Core EPAs); NCCPA PANCE Content Blueprint. VMS is not affiliated with these organizations. Updated: 2026-10-11.