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Test Code GFAPP Glial Fibrillary Acidic Protein (GFAP), Plasma


Shipping Instructions


Send refrigerated.



Specimen Required


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.


Secondary ID

623425

Useful For

As a biomarker of astrocyte activation related to brain injury and various neurological disorders

Method Name

Chemiluminescent Enzyme Immunoassay (CLEIA)

Reporting Name

Glial Fibrillary Acidic Protein, P

Specimen Type

EDTA Plasma

Specimen Minimum Volume

Plasma: 0.75 mL

Specimen Stability Information

Specimen Type Temperature Time
EDTA Plasma Refrigerated (preferred) 14 days
  Frozen  90 days
  Ambient  72 hours

Reject Due To

Gross hemolysis Reject
Gross lipemia Reject
Gross icterus Reject

Clinical Information

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

<40 years: ≤32.6 pg/mL

40-49 years: ≤50.5 pg/mL

50-59 years: ≤67.5 pg/mL

60-69 years: ≤90.3 pg/mL

≥ 70 years: ≤120.8 pg/mL

Interpretation

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.

CPT Code Information

83520  

LOINC Code Information

Test ID Test Order Name Order LOINC Value
GFAPP Glial Fibrillary Acidic Protein, P 97604-3

 

Result ID Test Result Name Result LOINC Value
GFAPP Glial Fibrillary Acidic Protein, P 97604-3