Glial Fibrillary Acidic Protein (GFAP) Alpha IgG Antibody, Serum — Qualitative
A qualitative blood test for GFAP IgG antibodies, which can support evaluation for neurologic immune disorders when interpreted with symptoms and other tests.
["A positive result may support evaluation for a rare autoimmune neurologic condition, but it is not diagnostic by itself."]
Key facts at a glance
- LOINC
- 93424-0
- Short code
- GFAP alpha IgG Ser Ql CBA IFA
- Synonyms
- GFAP alpha IgG Ser Ql CBA IFA
- Category
- liver
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 44
- Ref high
- 147
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- cba-ifa
- CPT
- 84075
- SNOMED
- 27550007
- 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
What is this test?
This test checks a serum sample for antibodies directed against glial fibrillary acidic protein, or GFAP. GFAP is a protein found mainly in cells of the nervous system, and the test is reported as positive or negative.
Why might I need this test?
The test may be ordered when a clinician is evaluating unexplained neurologic symptoms that could be caused by an autoimmune or inflammatory condition. It is often considered alongside other antibody tests, cerebrospinal fluid testing, imaging, and the medical examination.
How is the test performed?
Blood is collected and separated to obtain serum. The laboratory then uses an antibody-detection assay to determine whether GFAP IgG is present, and the result is reported qualitatively as positive or negative.
How do I prepare for the test?
No special preparation or fasting is usually required. Follow any instructions provided by the ordering clinician or laboratory, and tell the healthcare team if you have an active infection, recently received immune treatments, or have other medical conditions that could affect interpretation.
Reference range
Adult: 44-147 U/LN/A
No special preparation required. Avoid fatty meals before the test if possible.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
A positive result may occur in autoimmune GFAP astrocytopathy, a rare immune-mediated nervous system disorder, and can also appear in other autoimmune neurologic conditions. It is not diagnostic on its own and must be interpreted with symptoms, examination findings, and supporting tests. A negative result does not completely exclude a neurologic immune disorder.
Short name
GFAP alpha IgG antibody, serum (qualitative)
Frequently asked questions
What does a positive GFAP IgG antibody result mean?
Is this the same as a cerebrospinal fluid test?
Does a negative result rule out an autoimmune neurologic disorder?
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