From the Guidelines
GFAP is a crucial biomarker for diagnosing autoimmune GFAP astrocytopathy, and its detection in cerebrospinal fluid (CSF) or serum is essential for proper diagnosis and management, as stated in the 2021 study by Abboud et al. 1.
Key Points for GFAP Presentation and Diagnosis
- GFAP typically presents as elevated levels in CSF or serum in conditions such as traumatic brain injury, stroke, neuromyelitis optica spectrum disorders (NMOSD), and autoimmune GFAP astrocytopathy.
- Diagnosis involves measuring GFAP levels through enzyme-linked immunosorbent assay (ELISA) or other immunoassays, with normal serum levels typically below 0.1 ng/mL, as suggested by the study 1.
- Elevated levels above this threshold suggest astrocyte damage or inflammation.
- For GFAP autoimmune astrocytopathy specifically, diagnosis requires detection of GFAP-IgG antibodies in CSF (more sensitive than serum testing), along with compatible clinical presentation and MRI findings showing characteristic radial enhancement patterns in the brain or longitudinally extensive myelitis, as proposed by the 2021 study 1.
Importance of Early Diagnosis and Treatment
- Early diagnosis is critical as prompt immunotherapy with high-dose corticosteroids (methylprednisolone 1000 mg daily for 3-5 days), followed by oral prednisone taper, can significantly improve outcomes.
- For refractory cases, second-line therapies include rituximab (375 mg/m² weekly for 4 weeks) or cyclophosphamide.
- GFAP testing should be considered in patients with unexplained encephalitis, myelitis, or optic neuritis, especially when conventional testing is negative, as recommended by the study 1.
Clinical Relevance of GFAP
- GFAP is a cytoplasmic antigen associated with intermediate filaments, and its clinical relevance varies according to presentation, as stated in the 2021 study 1.
- GFAP-IgG antibodies are considered clinically relevant in patients presenting with typical radiological findings (perivascular radial enhancement), as proposed by the study 1.
From the Research
GFAP Presentation and Diagnosis
- GFAP is a highly brain-specific protein that is expressed in large quantities in astrocytes and has important functions in terms of maintaining and stabilizing the cytoskeleton 2
- After traumatic brain injury (TBI), plasma concentration of glial fibrillary acidic protein (GFAP) correlates with intracranial injury visible on CT scan 3
- Acute intracerebral hemorrhage leads to an immediate mechanical destruction of astroglial cells with the subsequent release of GFAP into the extracellular space and the bloodstream 2
- Analysis of blood GFAP concentrations using prototype assays on a point-of-care platform within 24 h of injury might improve detection of TBI and identify patients who might need subsequent MRI and follow-up 3
Diagnostic Marker of Cerebral Hemorrhage
- Increased GFAP values could indicate intracerebral hemorrhage in the early hours after stroke 2
- GFAP release does not occur before 6-12 h after symptom onset in ischemic stroke, making it a potential diagnostic marker for cerebral hemorrhage 2
- The discriminative ability of GFAP to identify MRI abnormalities in patients with normal CT findings has been assessed, with an area under the ROC curve (AUC) of 0·777 (95% CI 0·726-0·829) over 24 h 3
Comparison with Other Biomarkers
- There is no direct comparison with other biomarkers in the provided studies, but GFAP has been shown to be a useful marker for diagnosing and monitoring TBI 3, 2
- Other studies have compared the effects of different treatments, such as hypertonic saline and mannitol, on intracranial pressure in TBI patients, but these do not directly relate to GFAP presentation and diagnosis 4, 5, 6