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Glial Fibrillary Acidic Protein (GFAP) in Cerebrospinal Fluid by Line Blot Immunoassay

Published: August 9, 2026Updated: August 16, 2026

This test measures a protein found in certain brain cells called astrocytes. It helps detect conditions that may cause swelling or damage in the brain or spinal cord.

Quick summary

["GFAP can signal potential brain injuries or diseases that affect glial cells."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
94383-7
Short code
Glial nuc type 1 IgG CSF Ql Line blot
Synonyms
Glial nuc type 1 IgG CSF Ql Line blot
Category
chemistry
Sample
csf
Container
Sterile tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
line-blot
CPT
82784
Specimen volume
1-2 mL
Stability
Immediate analysis required, Refrigerated: 1h
Hemolysis max
200
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your doctor may order this test if you have symptoms like sudden headaches, confusion, seizures, or neurological issues that could suggest conditions such as brain tumors, stroke, or traumatic brain injury. It’s also used in diagnosing certain types of brain inflammation or bleeding.

What Does the Test Measure?

GFAP is a protein produced by a type of supportive brain cell called astrocytes. Elevated levels in cerebrospinal fluid (CSF) may indicate damage or abnormal activity in these cells.

How Is the Test Performed?

A small amount of CSF is collected through a procedure called a lumbar puncture (spinal tap). The sample is then analyzed using a line blot immunoassay to detect GFAP levels.

What Are Possible Results?

Results are qualitative (positive or negative) rather than numeric. High levels of GFAP in CSF may suggest conditions like brain tumors, encephalitis, or traumatic brain injury.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: GFAP in CSF is primarily used as a biomarker for detecting and diagnosing conditions that cause glial cell damage or inflammation in the central nervous system. Elevated levels can support a diagnosis of brain tumors (such as gliomas), subarachnoid hemorrhage, or other neurological disorders affecting astrocytes.

Short name

GFAP CSF (Line Blot)

Frequently asked questions

What does a positive result mean?
A positive result (detecting GFAP) may indicate abnormal brain or spinal cord activity, such as swelling, bleeding, or tumors. Your doctor will discuss the next steps based on your symptoms and test results.
Can this test be done at home?
No, this test requires a medical procedure (lumbar puncture) and is performed in a clinical setting by trained professionals.
How long does it take to get results?
Results are typically available within a few days after the sample is collected and analyzed.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy