Rules-Based Medicine

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Glial Fibrillary Acidic Protein (GFAP)

Ultrasensitive Immunoassay


Rules-Based Medicine’s (RBM) internally developed and manufactured ultrasensitive immunoassay to glial fibrillary acidic protein (GFAP) based on the Simoa® bead technology can accurately quantitate sub-pg/mL levels of GFAP in human serum and plasma.

GFAP is a type III intermediate filament produced mainly by astrocytes, other glial cells, and neural stem cells. There are currently 10 splice isoforms identified, with the following found in humans: GFAPα, ꞵ, δ, ζ, κ, Δ135, D164, Δexon6, and Δexon 7. GFAPα is the most abundant and well-studied isoform. GFAP forms homopolymeric and heteroploymeric filaments with other type III intermediate filaments such as nestin, synemin, and vimentin. To date, the function of GFAP has not been fully elucidated, although it has been linked to various cell functions, such as migration, motility, mitosis, cell integrity, and cell signaling. GFAP is a marker for mature astrocytes and is elevated when astrocytes become activated during disease states. Due to these observations, GFAP is an emerging biomarker for several neurological diseases.

GFAP increases have been identified in Alzheimer’s, Parkinson’s, Huntington’s, after brain injury, epilepsy, and neurological cancers. Several studies have indicated the potential of GFAP as a biomarker for traumatic brain injury, which has continuously suffered setbacks for clinical therapy due to, in part, the lack of a robust diagnostic marker. It has proven useful to predict CT findings and pathological alterations, shown that elevation post-trauma can define disease severity, and may correlate to patient outcomes. Interestingly, because of the crosstalk between the nervous and immune systems, GFAP may play further roles in immune regulation. RBM’s Simoa GFAP assay is a sensitive clinical research tool for monitoring GFAP levels in human subjects.


Swiss-Prot Accession Number: P14136

Alternate names for this biomarker include:


Simoa™ Services
Biomarker LLOQ*
(Serum and Plasma)
(Undiluted Samples)
Volume Required
Serum or plasma Other fluids**
Glial Fibrillary Acidic Protein (GFAP) 0.70 pg/mL 0.175 pg/mL 100 µL 150 µL

* Lower limit of quantitation (LLOQ) represents the lowest amount of an analyte that can be quantitatively determined with acceptable precision. LLOQ is determined by performing 2-fold serial dilutions of Standard to be tested in triplicate over three runs. The percent coefficient of variation (CV) is calculated for each of the dilution replicates, and the LLOQ is determined as the concentration at which the CV is 30%.

** Cerebrospinal fluid, urine, tissue culture supernatants,  bronchoalveolar lavage, synovial fluid, tissue extracts, tears, skin washings, etc.

All assay services are performed in our CLIA-certified laboratory.
Intended for Research Use Only.