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Glial Fibrillary Acid Protein (GFAP) in Cerebrospinal Fluid (CSF) by Immunoassay

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

This test measures the level of glial fibrillary acidic protein (GFAP), a protein produced by certain types of brain cells called astrocytes. It helps assess for conditions affecting the brain’s protective covering or blood-brain barrier.

Quick summary

["GFAP levels in CSF can signal potential brain injuries or diseases."]

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

Key facts at a glance

LOINC
105327-1
Short code
GFAP Bld IA-mCnc
Synonyms
GFAP Bld IA-mCnc
Category
chemistry
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ia
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
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 bleeding, swelling, or inflammation in the brain. It’s also used in diagnosing conditions such as subarachnoid hemorrhage, brain tumors, or multiple sclerosis.

What Does the Test Involve?

A small amount of cerebrospinal fluid (CSF) is collected through a procedure called a lumbar puncture (spinal tap). The fluid is then sent to a lab for testing. GFAP is measured using an immunoassay method to detect its presence.

What Are Common Results?

Results are not typically provided in absolute numbers since reference ranges vary by lab and method. Instead, doctors compare your result to what’s expected for a healthy individual or to your previous results if retested.

What Does an Abnormal Result Mean?

Elevated GFAP levels in CSF often indicate conditions like brain bleeding, inflammation, or damage to the brain’s protective layers. Your doctor will discuss these findings with you based on your symptoms and other test results.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: GFAP in CSF is primarily used to identify acute brain injuries or certain neurological disorders. It’s especially valuable in cases where other tests may not provide clear answers, such as ruling out bleeding in the brain or detecting early signs of brain tumors.

Short name

GFAP CSF

Frequently asked questions

What does a high GFAP level in CSF usually indicate?
A high GFAP level may suggest conditions like traumatic brain injury, subarachnoid hemorrhage, or certain brain infections. However, it’s not definitive on its own—your doctor will review it alongside your symptoms and other test results.
Can GFAP levels change over time?
Yes, GFAP levels can fluctuate depending on the underlying condition. If you’re retested, your doctor may compare results to track changes or monitor progression of a condition.
Is this test painful?
The lumbar puncture procedure involves a small needle inserted into your lower back. You may feel pressure or discomfort, but it’s generally well-tolerated. Numbing medication is often used to minimize pain.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

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