CSF ANALYSIS INTERPRETATION

Composition of Normal CSF

Protein - 15 - 45 mg/dL Glucose - 50 - 80 mg/dL Urea - 6.0 - 16 mg/dL Uric acid - 0.5 - 3.0 mg/dL Creatinine - 0.6 - 1.2 mg/dL Cholesterol - 0.2 - 0.6 mg/dL Ammonia - 10 – 35 μg/dL

Composition of Normal CSF Sodium - 135 – 150 mEq/L Potassium - 2.6 – 3.0 mEq/L Chloride - 115 – 130 mEq/L Magnesium - 2.4 – 3.0 mEq/L Cells - 0 – 5 Lymph/μL

Characteristics of normal CSF• Color - Colorless• PH - 7.28 – 7.32• Appearance - Clear• Sp. Gravity - 1.003 – 1.004• No clot formation on standing• Total solids - 0.85 – 1.70 g/dL• PO2 - 40 – 44 mmHg

Diagnosis by CSF• High sensitivity, high specificity– Bacterial, TB, and fungal meningitis

• High sensitivity, moderate specificity– Viral meningitis, SAH, CNS syphilis, abscess

• Moderate sensitivity, high specificity–Meningeal malignancy

• Moderate sensitivity, moderate specificity– Intracranial hemorrhage, viral encephalitis,

subdural hematoma

Xanthochromia• Pink, orange, or yellow discoloration• RBC lysis or hemoglobin breakdown• May be seen within hours of LP• Peak intensity at 24 - 36 hours• RBC > 6000/μL (SAH, ICH, infarct, traumatic)• Oxyhemoglobin, bilirubin, increased protein• Carotinoids, melanin, rifampin therapy

Reference Intervals for CSFCell type Adults(%) Neonates(%)

Lymphocytes 62 20Monocytes 36 72Neutrophils 2 3Histiocytes Rare 5Ependymal Rare RareEosinophils Rare Rare

Increased Neutrophils in CSF• Meningitis (bacterial, early TB, fungal)• Other infections• Following seizures• Following CNS hemorrhage• Following CNS infarct• Reaction to repeated LP• Foreign materials• Metastatic tumor

Increased Lymphocytes in CSF• Meningitis (aseptic, viral, L monocytogenes)• Parasitic infections• Degenerative disorders– Encephalopathy due to drugs, GBS

• Other inflammatory conditions– Sarcoidosis, polyneuritis, periarteritis involving

the CNS

Increased CSF Total Protein

• Increased blood-CSF permeability–Meningitis (bacterial, fungal, TB)– Hemorrhage (SAH, ICH)– Endocrine disorders–Mechanical obstruction (tumor, disc, abcess)– Neurosypilis, MS, CVD

•Causes of decreased CSF glucose• Increased CSF glucose is of no clinical

significance.• Meningitis-Bacterial, fungal tubercular and

syphilitic meningitis. • Tumors involving the meninges.• Subarachnoid hemorrhage.• Cerebral ameobiasis.

Bacterial Meningitis• 0 - 1m: Group B strept & E. coli (GNR)• 1m - 5y: H. influenzae• 5 - 29y: N. meningitidis• >29y: S. pneumoniae• Listeria monocytogenes common in

newborns, elderly, and other immunocompromised hosts

Test Appearance Pressure WBC/μL Protein mg/dL

Glucose mg/dL

Chloride

Normal CSF

Clear 90 – 180 mm

0-8 lymph. 15-45 50-80 115-130 mEq/L

Acute bacterial meningitis

Turbid Increased 1000 -10000

100 – 500 < 40 Decreased

Viral meningitis

Clear Normal to moderate increase

5-300, rarely >1000

Normal to mild increased

Normal Normal

Tubercular meningitis

Slightly opaque cobweb formation

Increased/ decreased, spinal block

100-600 mixed or lymph.

50-300 due to spinal block

Decreased Decreased

Fungal meningitis

Clear Increased 40-400 mixed

50-300 Decreased Decreased

Acute syphilitic

Clear Increased About 500 lymph

Increased but <100

Normal normal