Glial Fibrillary Acid Protein (GFAP) in Serum by Immunoblot (Screening)
This test measures a protein produced by glial cells in the brain, which may help detect conditions affecting the brain’s protective covering or blood-brain barrier.
A GFAP test may help identify brain injuries or diseases that disrupt normal brain function.
Key facts at a glance
- LOINC
- 94382-9
- Short code
- Deprecated Glial nuc type 1 IgG Ser Ql Line blot
- Synonyms
- Deprecated Glial nuc type 1 IgG Ser Ql Line blot
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- line-blot
- CPT
- 82784
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
Why This Test Might Be Ordered
Your doctor may recommend this test if you’ve experienced symptoms like sudden confusion, severe headaches, seizures, or neurological issues that could suggest a brain injury, inflammation, or other neurological condition. It’s often used alongside other tests to support a diagnosis of conditions such as brain tumors, traumatic brain injury, or certain types of encephalitis.
What to Expect Before the Test
No special preparation is needed. You’ll provide a blood sample, typically drawn from a vein in your arm. If you’re on blood thinners, let your doctor know before the test.
What the Test Results Mean
Elevated levels of GFAP may indicate brain damage or inflammation, but results alone don’t confirm a diagnosis. Your doctor will review the test with other clinical findings, imaging results, and symptoms to determine the next steps.
Common Conditions Monitored
This test is primarily used to screen for conditions like brain tumors, subarachnoid hemorrhage, traumatic brain injury, or certain types of encephalitis. It’s not a routine screening test for healthy individuals.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
GFAP is a sensitive marker for detecting acute brain injury or inflammation. Elevated levels can signal conditions that require urgent medical attention, such as bleeding in the brain or severe infections. However, false positives or negatives can occur, so this test is used as part of a broader diagnostic evaluation rather than alone.
Short name
GFAP Screen
Frequently asked questions
What does a positive or elevated GFAP result mean?
Can lifestyle changes or medications affect GFAP levels?
How soon after a brain injury would I expect to get abnormal GFAP results?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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