Lumbar Puncture (LP) Interpretation of Cerebrospinal Fluid

This short reference guide provides generic information that may guide initial interpretation of cerebrospinal fluid (CSF) studies but should not be used alone for determination of normal or abnormal results. For further information, see Lumbar Puncture.

The patient’s specific factors (which are beyond the scope of this brief guide), as well as the reference range variability among different laboratories, must be considered by the treating provider when obtaining and interpreting tests. ^[1]

Caution is warranted in the routine clinical use of existing clinical predictive rules for bacterial meningitis until high diagnostic performance is prospectively validated. ^[2]

Approximately 90% of immunocompetent patients with culture-proven meningitis have CSF findings characteristic of acute community-acquired bacterial meningitis. Immunocompromised patients and patients with tuberculosis meningitis may present with acellular / low – white blood cell (WBC) – CSF meningitis. ^{[3, 4]}

Normal results in adults

See the list below:

• Appearance: Clear

• Opening pressure: 10-20 cm H₂ O

• 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

See the list below:

• Appearance: Clear, cloudy, or purulent

• Opening pressure: Elevated (>25 cm H₂ O)

• 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)

Consider additional tests: CSF Gram stain and cultures, blood cultures, CSF bacterial antigens, CSF polymerase chain reaction (PCR), others depending on clinical findings

Aseptic (viral) meningitis

See the list below:

• Appearance: Clear

• Opening pressure: Normal or elevated

• WBC count: 10-1000 cells/µL (lymph but 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 (eg, herpes simplex virus [HSV], varicella-zoster virus [VZV]), others depending on clinical findings

Fungal meningitis

See the list below:

• Appearance: Clear or cloudy

• Opening pressure: Elevated

• WBC count: 10-500 cells/µL

• Glucose level: Low

• Protein level: Elevated

Consider additional tests: CSF Gram stain and cultures, blood cultures, CSF bacterial antigens, CSF PCR, CSF India ink, others depending on clinical findings

Tuberculosis

See the list below:

• Appearance: Clear or opaque

• Opening pressure: Elevated

• WBC count: 50-500 cells/µL (early PMN then lymph)

• 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, others depending on clinical findings

Subarachnoid hemorrhage

See the list below:

• 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

Consider additional tests: CSF Gram stain and cultures, others depending on clinical findings

Multiple sclerosis

See the list below:

• Appearance: Clear

• Opening pressure: Normal

• WBC count: 0-20 cells/µL (lymph)

• Glucose level: Normal

• Protein level: Mildly elevated (45-75 mg/dL)

Consider additional tests: Oligoclonal band analysis (serum and CSF), others depending on clinical findings

Guillain Barré syndrome

See the list below:

• Appearance: Clear or xanthochromia

• Opening pressure: Normal or elevated

• WBC count: Normal or elevated

• Glucose level: Normal

• Protein level: Elevated

Consider additional tests: Others depending on clinical findings