Test Id : GFAPP
Glial Fibrillary Acidic Protein (GFAP), Plasma
Useful For
Suggests clinical disorders or settings where the test may be helpful
As a biomarker of astrocyte activation related to brain injury and various neurological disorders
Highlights
This assay measures glial fibrillary acidic protein in human plasma.
Method Name
A short description of the method used to perform the test
Chemiluminescent Enzyme Immunoassay (CLEIA)
NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.
Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test
Aliases
Lists additional common names for a test, as an aid in searching
Alzheimer
Alzheimer's Disease
Dementia
GFAP
Specimen Type
Describes the specimen type validated for testing
EDTA Plasma
Shipping Instructions
Send refrigerated.
Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing
Patient Preparation:
Fasting: 8 hours, required
Supplies: Sarstedt Aliquot Tube, 5 mL (T914)
Collection Container/Tube: Lavender top (EDTA)
Submission Container/Tube: Plastic vial
Specimen Volume: 1 mL plasma
Collection Information: Centrifuge and aliquot plasma into a plastic vial.
Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the testing laboratory. The minimum volume is sufficient for one attempt at testing.
Plasma: 0.75 mL
Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected
| Gross hemolysis | Reject |
| Gross lipemia | Reject |
| Gross icterus | Reject |
Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| EDTA Plasma | Refrigerated (preferred) | 14 days | |
| Ambient | 72 hours | ||
| Frozen | 90 days |
Useful For
Suggests clinical disorders or settings where the test may be helpful
As a biomarker of astrocyte activation related to brain injury and various neurological disorders
Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Glial fibrillary acidic protein (GFAP) functions as the primary intermediate filament protein within the astrocyte cytoskeleton. Under pathological conditions such as inflammation, neurodegeneration or traumatic brain injury, GFAP expression is upregulated resulting in morphological alterations of astrocytes through reorganization of intermediate filaments. Increased GFAP concentrations correlate with the severity of neural damage, leading to structural hypertrophy of reactive astrocytes. In cases of severe and widespread brain injuries, astrocytes undergo extensive proliferation and form physical and chemical barriers surrounding lesion sites. This response is critical for containing damage and preventing its propagation to healthy tissues. The upregulation of GFAP acts as a marker of astrocyte activation following neural injury. GFAP is primarily localized intracellularly, but various mechanisms can induce its release into the cerebrospinal fluid (CSF) and subsequent entry to the bloodstream. The mechanism leading to release of GFAP into biofluids is not fully understood. Mechanisms such as astrocyte damage or death and neuroinflammation have been proposed to contribute to the release GFAP into the CSF and subsequently into the bloodstream. GFAP is a brain-specific protein with limited secretion into biofluids under physiological conditions, reinforcing its relevance as a neurodegenerative brain disease biomarker.
Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
<40 years: < or =32.6 pg/mL
40-49 years: < or =50.5 pg/mL
50-59 years: < or =67.5 pg/mL
60-69 years: < or =90.3 pg/mL
> or = 70 years: < or =120.8 pg/mL
Interpretation
Provides information to assist in interpretation of the test results
Increased glial fibrillary acidic protein (GFAP) concentrations have been observed during brain injury and in various neurological disorders. Currently, there are no disease-specific thresholds for interpretation; thus, results should be assessed according to established reference intervals. Some potential uses of GFAP are described below.
In traumatic brain injury (TBI), GFAP concentrations are increased in patients following mild to moderate TBI, and it may predict an unfavorable outcome.(1) GFAP has been shown to be detectable within one hour of injury, continues to rise and appears to peak within 20 to 24 hours, and then declines over 72 hours with a biological half-life of 24 to 48 hours.(2,3)
Glial fibrillary acidic protein concentrations have been reported to be higher in individuals with multiple sclerosis (MS) compared to healthy controls and individuals with non-inflammatory neurological disease.(4,5) Plasma GFAP concentrations have been shown to correlate with the severity of disability in patients with MS.(4,5)
In stroke, blood GFAP may be indicative of microglial injury as a result of intracerebral hemorrhage in individuals presenting with acute stroke symptoms. In this context, GFAP concentrations were higher in individuals with intracerebral hemorrhage than in patients with ischemic stroke.(6)
Increased blood GFAP concentrations have been detected in individuals with Alzheimer disease (AD), with rising levels observed at the preclinical phase of the disease.(7) Higher GFAP concentrations have been associated with an increased risk for future progression to dementia and a steeper cognitive decline.(8) In individuals with mild cognitive impairment, GFAP concentrations have been reported to predict future conversion to AD dementia.(7)
In individuals with autoimmune glial fibrillary acidic protein astrocytopathy (GFAP-A), an antibody-related astrocytic disease for which a specific GFAP antibody serves as a biological marker, elevations of plasma GFAP may be observed.(9) However, measurement of plasma GFAP is not recommended as part of the diagnostic evaluation for this rare autoimmune disease. In this context, measurement of GFAP-IgG antibodies in cerebrospinal fluid is recommended for the evaluation of individuals suspected of having GFAP-A.
Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Glial fibrillary acidic protein results must be interpreted in conjunction with other diagnostic tools, such as neurological examination, neurobehavioral tests, imaging, and routine laboratory tests.
Results obtained with different assay methods or kits may be different and cannot be used interchangeably.
All immunometric assays can, on rare occasions, be subject to a hooking effect at extremely high analyte concentrations (false-low results), heterophilic antibody interference (false-high results), or autoantibody interference (unpredictable effects). If the laboratory result does not fit the clinical picture, these possibilities should be considered.
Clinical Reference
Recommendations for in-depth reading of a clinical nature
1. Abdelhak A, Foschi M, Abu-Rumeileh S, et al. Blood GFAP as an emerging biomarker in brain and spinal cord disorders. Nat Rev Neurol. 2022;18(3):158-172
2. Papa L, Brophy GM, Welch RD, et al. Time course and diagnostic accuracy of glial and neuronal blood biomarkers GFAP and UCH-L1 in a large cohort of trauma patients with and without mild traumatic brain injury. JAMA Neurol. 2016;73(5):551-560
3. Thelin EP, Zeiler FA, Ercole A, et al. Serial sampling of serum protein biomarkers for monitoring human traumatic brain injury dynamics: A systematic review. Front Neurol. 2017;8:300
4. Hogel H, Rissanen E, Barro C, et al. Serum glial fibrillary acidic protein correlates with multiple sclerosis disease severity. Mult Scler. 2020;26(2):210-219
5. Ayrignac X, Le Bars E, Duflos C, et al. Serum GFAP in multiple sclerosis: correlation with disease type and MRI markers of disease severity. Sci Rep. 2020;10(1):10923
6. Foerch C, Curdt I, Yan B, et al. Serum glial fibrillary acidic protein as a biomarker for intracerebral haemorrhage in patients with acute stroke. J Neurol Neurosurg Psychiatry. 2006;77(2):181-184
7. Oeckl P, Halbgebauer S, Anderl-Straub S, et al. Glial fibrillary acidic protein in serum is increased in Alzheimer’s disease and correlates with cognitive impairment. J Alzheimers Dis. 2019;67(2):481-488. doi:10.3233/JAD-180325
8. Cicognola C, Janelidze S, Hertze J, et al. Plasma glial fibrillary acidic protein detects Alzheimer pathology and predicts future conversion to Alzheimer dementia in patients with mild cognitive impairment. Alzheimers Res Ther. 2021;13(1):68. Published 2021 Mar 27. doi:10.1186/s13195-021-00804-9
9. Huang J, Huang W, Zhou R, Lin W, Chen T, Long Y. Detection and significance of glial fibrillary acidic protein antibody in autoimmune astocytopathy and related diseases. Ann Transl Med. 2023;11(7):288. doi:10.21037/atm-19-330
Method Description
Describes how the test is performed and provides a method-specific reference
The Lumipulse G GFAP Immunoreaction is an assay system for the quantitative measurement of glial fibrillary acidic protein (GFAP) in plasma specimens based on chemiluminescent enzyme immunoassay technology by a specific two-step immunoassay method on the Lumipulse G System. The specimen and assay-specific diluent are added to the antibody-coated particle solution. The GFAP in the specimen specifically binds to anti-GFAP monoclonal mouse antibody on the particles and antigen-antibody immunocomplexes are formed. The particles are washed and rinsed to remove unbound materials. Alkaline phosphatase-labeled anti-GFAP monoclonal antibodies specifically bind to immunocomplexes on the particles. The particles are washed and rinsed to remove unbound materials. The substrate solution is added and mixed with the particles. 3-(2'-Spiroadamantyl)-4-methoxy-4-(3"-phosphoryloxy)-phenyl-1,2-dioxetane (AMPPD) contained in the substrate solution is dephosphorylated by the catalysis of alkaline phosphatase indirectly conjugated to particles. Luminescence (at a maximum wavelength of 477 nm) is generated by the cleavage reaction of dephosphorylated AMPPD. The luminescent signal reflects the amount of GFAP present in the sample.(Package insert: Lumipulse G GFAP. Fujirebio Inc; ver 1, 07/2024)
PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information
Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.
Wednesday
Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.
Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location
Indicates the location of the laboratory that performs the test
Fees :
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Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.
CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
CPT codes are provided by the performing laboratory.
CPT codes are provided by the performing laboratory.
83520
LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.
| Test Id | Test Order Name | Order LOINC Value |
|---|---|---|
| GFAPP | Glial Fibrillary Acidic Protein, P | 97604-3 |
| Result Id | Test Result Name |
Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
|
|---|---|---|
| GFAPP | Glial Fibrillary Acidic Protein, P | 97604-3 |