What this test measures
CSF Routine Analysis examines the cerebrospinal fluid (CSF) obtained from a lumbar puncture. It reports physical appearance (clear, turbid, blood-stained, xanthochromic), cell counts (total and differential WBC, RBC), protein, glucose and sometimes lactate. CSF normally contains very few cells, low protein (<45 mg/dL), and glucose at about two-thirds the blood glucose level.
The profile of these basic parameters is highly informative: bacterial meningitis classically shows turbid CSF with neutrophilic pleocytosis, very high protein, and low glucose; viral meningitis shows lymphocytic pleocytosis with mildly raised protein and normal glucose; tubercular meningitis (very important in India) shows lymphocytic pleocytosis, very high protein, and low glucose; and subarachnoid haemorrhage shows red cells and xanthochromia.
Why it matters
Lumbar puncture is one of the most consequential bedside investigations in neurology and emergency medicine. India bears a significant burden of bacterial meningitis (especially in children), Japanese encephalitis, tubercular meningitis, and cryptococcal meningitis (in HIV/immunocompromised patients) — all of which need rapid CSF analysis for diagnosis and treatment.
The routine analysis is the first-line test on any CSF sample. It guides whether the case looks bacterial (start antibiotics immediately), viral (supportive care), tubercular (start ATT + steroids), or non-infective (search for other causes). It is also crucial in diagnosing subarachnoid haemorrhage when CT is negative, in workup of unexplained headaches with fever, and in evaluating multiple sclerosis, Guillain-Barré syndrome (which classically shows raised CSF protein with normal cells), and chronic neurological disease.
How to prepare
CSF is collected during a lumbar puncture performed by a doctor. You will be asked to lie on your side curled up or sit leaning forward. Local anaesthesia is given. Tell your doctor about any blood thinners (warfarin, DOACs, antiplatelets) — these often need to be stopped before the procedure. After the procedure, lie flat for several hours and drink plenty of fluids to reduce the risk of post-LP headache.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| CSF WBC (cells/µL)[1][2] | Adults: 0–5 lymphocytes · Neonates: up to 30 | Normal cellularity. | Pleocytosis. Neutrophil-predominant (>1000) → bacterial meningitis. Lymphocyte-predominant → viral, tubercular, fungal meningitis, autoimmune encephalitis. Eosinophil-predominant → parasitic infection. |
| CSF Protein (mg/dL) | 15–45 | Usually not clinically significant. | Mildly raised (45–100): viral meningitis, MS. Markedly raised (>100): bacterial meningitis, tubercular meningitis, Guillain-Barré (albuminocytologic dissociation — high protein with normal cells), spinal block. |
| CSF Glucose (mg/dL) | 40–80 (≈ 2/3 of simultaneous blood glucose) | Low CSF glucose (hypoglycorrhachia) — bacterial meningitis, tubercular meningitis, fungal meningitis (cryptococcal), carcinomatous meningitis. The ratio of CSF glucose to blood glucose <0.4 is informative. | High CSF glucose reflects high blood glucose (e.g., uncontrolled diabetes) — not a primary pathology. |
CSF profile in common neurological infections
| Diagnosis | WBC pattern | Protein | Glucose |
|---|---|---|---|
| Bacterial meningitis | >1000, neutrophils | Very high (100–500) | Low (<40) |
| Viral meningitis | 10–500, lymphocytes | Mildly high (50–100) | Normal |
| Tubercular meningitis | 50–500, lymphocytes | Very high (100–500) | Low (<40) |
| Cryptococcal (HIV) | Variable, lymphocytes | High | Low |
| Guillain-Barré syndrome | Normal (0–5) | Very high (>100) | Normal |
| Subarachnoid haemorrhage | RBCs, xanthochromia | Mildly high | Normal |
| Multiple sclerosis | Mildly high lymphocytes | Mildly high | Normal |
Frequently asked questions
Is lumbar puncture painful?
There is brief discomfort during local anaesthesia and a pressure sensation when the needle enters the space. Most patients describe it as uncomfortable but tolerable. Significant pain is uncommon with experienced operators.
How long does the result take?
Routine analysis (cells, protein, glucose) is usually available within 1–2 hours. Cultures take 24–72 hours; AFB stain and culture for TB take 6–8 weeks.
What is the most common complication?
Post-lumbar-puncture headache, which can occur in 10–30% of patients. It is usually self-limiting within a few days. Bleeding, infection and nerve injury are rare.
Do I need to fast?
No fasting required, but light food only. Tell the doctor about all medications, especially blood thinners and antiplatelets.
When should I avoid lumbar puncture?
Lumbar puncture should be avoided or done only after imaging if there are signs of raised intracranial pressure (papilloedema, focal neurological deficits, severe altered consciousness), bleeding disorders, or local skin infection at the puncture site.
Will I need a CT before LP?
CT brain is recommended before LP in adults with new neurological deficits, recent seizures, immunocompromise, papilloedema, or altered consciousness — to rule out a mass lesion that could make LP unsafe.
Related Autoimmune / Rheumatology tests
Tests commonly ordered alongside CSF ROUTINE ANALYSIS, or that help interpret an unexpected result.
Sources & references
- NIH MedlinePlus — Cerebrospinal Fluid (CSF) Analysis · accessed 2026-05-30T00:00:00.000Z
- NCBI StatPearls — Cerebrospinal Fluid Analysis · accessed 2026-05-30T00:00:00.000Z
- IDSA — Practice Guidelines for Bacterial Meningitis · accessed 2026-05-30T00:00:00.000Z
- Mayo Clinic Labs — Cerebrospinal Fluid Analysis · accessed 2026-05-30T00:00:00.000Z
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