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Cerebrospinal fluid (CSF) analysis

Body Fluids · also called CSF routine, Lumbar puncture fluid

What it measures

Examines fluid from lumbar puncture for appearance, cells, glucose, protein and organisms. It is essential for diagnosing meningitis, encephalitis and subarachnoid hemorrhage.

Specimen and preparation

Specimen: CSF in 3–4 sterile numbered tubes
Tube: Csf top
Preparation: Deliver immediately at room temperature (never refrigerate for culture); draw paired blood glucose.

Reference range

Group	Range
Appearance	Clear, colourless
WBC, adult	0–5 cells/µL
Glucose	45–80 (about 60% of blood) mg/dL
Protein	15–45 mg/dL
Opening pressure	10–20 cm H₂O

Reference ranges differ between laboratories, methods and populations. Always use the range printed on your own lab report.

Causes of high values

Bacterial meningitis: neutrophils, very high protein, low glucose
Viral meningitis: lymphocytes, normal glucose
TB/fungal: lymphocytes, high protein, low glucose
Xanthochromia: subarachnoid hemorrhage
High protein alone: Guillain-Barré syndrome

Causes of low values

Low glucose: bacterial, TB or fungal meningitis, carcinomatous meningitis

Method

Cell count (chamber/analyser), glucose, protein, Gram stain, culture, PCR, cryptococcal antigen, cytology

Good to know

Positive Gram stain, culture, blasts or malignant cells in CSF are critical results.

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