Glial Fibrillary Acidic Protein

GFAP belongs to the family of intermediate filament proteins that form the cytoskeletal scaffolding of astrocytes. Under normal physiological conditions, GFAP is expressed at low levels and remains confined within intact astrocytes. When astrocytes are damaged — through trauma, ischemia, hemorrhage, or neurodegeneration — GFAP and its breakdown products are released into the interstitial fluid, cross the disrupted blood-brain barrier, and become detectable in peripheral blood. This release mechanism is what makes GFAP valuable as a non-invasive biomarker of brain injury.

The FDA cleared the first blood-based GFAP test (in combination with UCH-L1) in 2018 for evaluating patients with suspected mild traumatic brain injury (mTBI). This test helps clinicians determine which head-injured patients are unlikely to have intracranial lesions visible on CT scan, potentially reducing unnecessary CT imaging by approximately one-third. GFAP levels typically peak within hours of injury and may remain elevated for several days, providing a clinically actionable detection window.

Beyond acute TBI, GFAP is under active investigation as a biomarker for other neurological conditions. Elevated GFAP levels have been observed in patients with intracranial hemorrhage (where GFAP may help differentiate hemorrhagic from ischemic stroke), multiple sclerosis, and certain neurodegenerative diseases. The protein's specificity to astrocytes, which are central nervous system-restricted cells, gives GFAP an inherent tissue-specificity advantage over more broadly expressed injury markers.

Prevena Health is investigating whether continuous GFAP monitoring may support earlier identification of neurological injury. Current clinical GFAP testing requires a blood draw in an emergency or hospital setting, which means that detection depends on the patient first reaching a healthcare facility. For populations at elevated risk of head injury — such as athletes, military personnel, or elderly individuals prone to falls — continuous ambulatory monitoring aims to provide a safety net that captures GFAP elevations as they occur.

Prevena's platform is being designed to detect changes in circulating protein biomarkers through a skin-worn sensor. In the context of GFAP, this approach may support research into the kinetics of astrocytic injury markers following concussive and subconcussive impacts, and could contribute to a more complete understanding of how GFAP levels evolve in real-world, non-clinical environments.