GFAP (Glial fibrillary acidic protein)
GFAP (glial fibrillary acidic protein) is the main structural fiber inside mature astrocytes. (Astrocytes are a type of brain support cell.) It is a marker of 'reactive astrogliosis'. That just means astrocytes are responding to injury. Ultra-sensitive assays now let labs measure GFAP in your blood plasma. There, it rises across the Alzheimer's continuum. It is even detectable early, in people who are amyloid-positive but still cognitively normal. Plasma GFAP separates amyloid-PET-positive from negative status. It does so more accurately than spinal-fluid GFAP. It is being tested as a complement to amyloid and tau markers, within the ATN framework. GFAP also rises after a traumatic brain injury. There, it is used clinically (with UCH-L1) for triage. But it is not specific to Alzheimer's. So read it alongside p-tau217 and amyloid biomarkers.
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Sources
- Benedet AL, Mila-Aloma M, Vrillon A, Ashton NJ, Pascoal TA, Lussier F, et al.. (2021). Differences Between Plasma and Cerebrospinal Fluid Glial Fibrillary Acidic Protein Levels Across the Alzheimer Disease Continuum. *JAMA Neurology*doi:10.1001/jamaneurol.2021.3671
- Pereira JB, Janelidze S, Smith R, Mattsson-Carlgren N, Palmqvist S, Teunissen CE, et al.. (2021). Plasma GFAP is an early marker of amyloid-beta but not tau pathology in Alzheimer's disease. *Brain*doi:10.1093/brain/awab223