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Background
The Glial Fibrillary Acidic Protein (GFAP) test is a diagnostic method to detect and quantify the GFAP. It is a protein which is found mainly in astrocytes of the central nervous system (CNS). This test is used as a significant biomarker in neurology and medicine because to GFAP is involved in astrocytic function, CNS structural integrity, and disease or injury response.
GFAP usually belongs to the CNS and is a component of the intermediate filament network in astrocytes. It provides structural support and maintains astrocytic function. When astrocytes are destroyed like during traumatic brain traumas, strokes, neurodegenerative conditions or other CNS disorders, GFAP gets released into the extracellular space. In situations when the blood-brain barrier is broken down, GFAP can enter into the circulation, and it is detectable in blood serum or plasma.
GFAP is a CNS-specific biomarker. It is used to detect glial malignancies and confirm gliosis in brain tissue. Advances in analytical methods like ELISA, chemiluminescent immunoassays, and mass spectrometry have allowed to detect in blood and CSF, increasing its potential for therapy. Protein increases may be detected by high sensitivity tests and makes GFAP test specific in acute and subacute CNS damage situations and in emergency and critical care.
The GFAP test is an effective method to identify and monitor a variety of CNS conditions. It is the first indicators that occur after a traumatic brain injury (TBI), observing the extent of astrocytic damage. It may differentiate between mild and moderate-to-severe TBIs. It is authorized by the FDA to use in the evaluation of mild TBI. Astrocytic injury leads to elevated levels of GFAP in both ischemic and hemorrhagic strokes. Chronic astrocytic activation in neurological conditions like Alzheimer’s, Parkinson’s, and ALS leads to continuous increases in GFAP. It is useful to monitor the development of the disease. Elevated levels of GFAP in the CSF of MS patients show astrocytic gliosis, which is an indicator of persistent lesions in this demyelinating condition. GFAP test is critical for the immunohistochemistry diagnosis of astrocytomas and glioblastomas, encephalitis, meningitis, or autoimmune astrocytopathy.
The GFAP test is an important biomarker to diagnose the astrocytic damage and understand CNS diseases because of its high specificity for astrocytes and reactivity to injury or disease.
Indications/Applications
GFAP test is used to detect the conditions like:
Traumatic Brain Injury (TBI): The levels of GFAP is connected with the severity of the brain injury with the increased levels in mild to severe cases of TBI than the mild cases. It is also used to differentiate the mild TBI from mild to severe injury specifically when the imaging results are not interpretable. GFAP and ubiquitin carboxyl-terminal hydrolase-L1 (UCH-L1) is used as a FDA approved biomarker to check the necessity of the head CT scan in mild TBI.
Stroke: It is used to diagnose the stroke as it increases the levels of GFAP. It indicates the astrocytic injury in both hemorrhagic stroke and ischemic stroke. Hemorrhagic strokes is more strongly linked with the increased level of GFAP. It is detected in early diagnosis and predict the severity of stroke and outcomes of patient.
Neurodegenerative disease: GFAP levels are linked to astrocytic activation and neuroinflammation in Alzheimer’s disease, Parkinson’s disease, and ALS. It may help to monitor the progression of disease. It differentiates between primary neurodegenerative diseases and other forms of dementia or encephalopathy.
Multiple Sclerosis (MS): GFAP levels in the cerebrospinal fluid (CSF) are linked to the progression of Multiple Sclerosis (MS), indicating the extent of astrocytic damage and gliosis in chronic MS lesions. Increased level of GFAP in CSF is linked with the progression of MS and severity of the disease.
Oncology: GFAP is used to detect and define astrocytic malignancies like astrocytomas and glioblastomas in tissue samples by using immunohistochemistry in oncology.
CNS infections and autoimmune diseases: CNS infections like encephalitis and meningitis can cause astrocytic damage which lead to increased GFAP levels in the CSF. Autoimmune astrcytopathy is caused by astrocytic inflammation and gliosis. It can be identified by checking the GFAP levels.
Other CNS diseases: GFAP level increased in cases of brain swelling which is caused by astrocytic injury in cerebral edema. In situations of cerebral hypoxia, GFAP levels can reflect the severity of astrocytic damage in Hypoxic-ischemic Encephalopathy.
The normal level of GFAP in serum is changes with the age and give below.
0 to 19 years – Not established
20 to 39 years – 0.00 to 57.40 pg/mL
40 to 49 years – 0.00 to 65.80 pg/mL
50 to 59 years – 0.00 to 87.10 pg/mL
≥60 years – 0.00 to 186.00 pg/mL
The normal level of GFAP in CSF: Below 10 pg/mL
The normal range for GFAP levels can differ on the type of sample, age and gender, the specific test used and the clinical setting.
Reference Range
Interpretation
Increased level of GFAP can indicate astrocytic activation, injury, or dysfunction because of the chronic or acute CNS pathology.
Mild elevation can lead to early-stage neurodegenerative diseases like Alzheimer’s disease, Parkinson’s disease, subclinical CNS injury or gliosis, low-grade astrocytic activation because of the chronic inflammation or minor trauma.
Moderate elevation can lead to disease like traumatic brain injury (TBI), acute exacerbations of neuroinflammatory disease like multiple sclerosis, autoimmune astrocytopathy, stroke, CNS infections like encephalitis or meningitis.
Severe elevation can lead to disease like severe TBI with astrocytic disruption, large infarcts or extensive hemorrhagic strokes, advanced neurodegenerative diseases with extensive gliosis, CNS tumors like astrocytomas, glioblastomas.
Collection And Panels
Sample type: Plasma or serum
Sample collection method: Venipuncture
Sample collection tube: serum-separating tube or gold top tube or plasma collection tube with lithium heparin or EDTA, lavender or green top tube
Sample volume: 2 to 5 mL
Sample type: Cerebrospinal fluid (CSF)
Sample collection method: Lumber puncture in sterile conditions
Sample collection tube: Sterile CSF collection tube
Sample volume: 1 to 2 mL
Sample storage: Blood samples must be centrifuges in 2 hours after the collection, Serum or plasma must be stored in 2 to 8 °C for 48 hours and -20 to -80 °C in frozen conditions for longer periods.
CSF samples must be stored or frozen at -80 °C immediately after the collection if there is a delay.
Unacceptable samples: Hemolyzed, clotted blood samples, contaminated CSF sample, or improper volume of sample
Modifying factors: GFAP levels are affected by several factors like time since injury, severity of CNS damage, laboratory variability, and comorbid conditions. The peak GFAP levels occur within hours of astrocytic injury and decline over days. Greater injury leads to higher GFAP levels. Non-CNS conditions can also affect GFAP levels.
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