Interpretation of CSF results from lumbar puncture (LP)
The outline below gives basic indication of patterns of disease to look for in CSF. However, note that CSF results should always be interpreted with the clinical picture in mind.
Reference ranges may vary between labs
Normal results in adults
Appearance: Clear
Opening pressure: 10-20 cmCSF
WBC count: 0-5 cells/µL
< 2 polymorphonucleocytes [PMN])
Normal cell counts do not rule out meningitis or any other pathology
Glucose level: >60% of serum glucose
Protein level: < 45 mg/dL
Consider additional tests: CSF culture, others depending on clinical findings
Bacterial meningitis
Appearance: Clear, cloudy, or purulent
Opening pressure: Usually elevated (>25 cmCSF)
WBC count: >100 cells/µL
>90% PMN
Partially treated cases may have as low as 1 WBC/µL
Glucose level: Low (< 40% of serum glucose)
Protein level: Elevated (>50 mg/dL)
Additional tests: CSF Gram stain and cultures, blood cultures, CSF bacterial antigens, CSF polymerase chain reaction (PCR) for common viruses
Viral meningitis
Appearance: Clear
Opening pressure: Normal or elevated
WBC count: 10-1000 cells/µL
Classically lymphocytes but may be PMN early
Glucose level: >60% serum glucose (may be low in HSV infection)
Protein level: Elevated (>50 mg/dL)
Consider additional tests: CSF Gram stain and cultures, blood cultures, CSF bacterial antigens, CSF PCR for herpes simplex virus (HSV), varicella-zoster virus (VZV) and other common virus such as adenovirus or enterovirus depending on area
Fungal meningitis
Appearance: Clear or cloudy
Opening pressure: Elevated
WBC count: 10-500 cells/µL
Glucose level: Low
Protein level: Elevated
Additional tests: CSF Gram stain and cultures, blood cultures, CSF bacterial antigens, CSF PCR, CSF India ink
Tuberculosis (TB)
Appearance: Clear or opaque
Opening pressure: Elevated
WBC count: 50-500 cells/µL
Early PMNs then lymphocytes
Glucose level: Low
Protein level: Elevated
Consider additional tests: CSF Gram stain and cultures, blood cultures, CSF bacterial antigens, CSF PCR, CSF tuberculosis culture/stain looking for acid fast bacilli (AFB)
Subarachnoid hemorrhage (SAH)
Appearance: Xanthochromia, bloody, or clear
Opening pressure: Elevated
WBC count: (1 additional WBC per 1000 RBCs is considered normal correction)
Glucose level: Normal
Protein level: Elevated
Additional tests: CSF Gram stain and culture, photospectometry to examine for xanthochromia
Multiple sclerosis (MS)
Appearance: Clear
Opening pressure: Normal
WBC count: 0-20 cells/µL (lymphocytes)
Glucose level: Normal
Protein level: Usually mildly elevated (45-75 mg/dL)
Additional tests: Oligoclonal bands (paired serum and CSF)
