Use
This test is used for the measurement of glial fibrillary acidic protein (GFAP) in serum.
Special Instructions
This test may exhibit interference when sample is collected from a person who is consuming a supplement with a high dose of biotin (also termed as vitamin B7 or B8, vitamin H, or coenzyme R). It is recommended to ask all patients who may be indicated for this test about biotin supplementation. Patients should be cautioned to stop biotin consumption at least 72 hours prior to the collection of a sample.
 
GFAP is a 50 k-Da intermediate filament protein that forms the structural backbone of astrocytes.2,5-7 Astrocytes represent approximately 35 percent of the cells in the central nervous system8,9 and serve as an integral part of the blood-brain barrier. These cells facilitate numerous interactions with other cells in the nervous system, including neurons. Astrocytes are central to the normal function of synapses and contribute to axonal metabolic maintenance through the regulation of ion homeostasis.10 Growing research supports the fundamental role of reactive astrocytosis in neurodegenerative disease with elevated GFAP expression as a primary marker.11 Following plasma membrane damage secondary to neurotrauma, GFAP is released into the interstitial fluid and enters the blood stream by crossing the blood-brain barrier, which is compromised following trauma12-14 or via the lymphatic system.13,15 There is a large body of published data on the utility of measuring CSF levels of GFAP.16-19 With the development of more sensitive assays, accurate measurement of serum levels of GFAP is now available. Increased levels of serum GFAP have been associated with cognitive decline and dementia status due to a number of pathologies.2,20-24
The formation of pathological GFAP aggregates in vivo can accompany lethal neurological disorders such as Alexander disease.5 Alexander disease is caused by various dominant heterozygous mutations in the gene encoding GFAP.25 The pathological hallmark of the disease is the formation of cytoplasmic aggregations in astrocytes.5 Owing to the rarity of the disease, studies investigating GFAP levels in the blood of individuals with Alexander disease are limited. One study found a modest elevation of GFAP levels in the serum of participants with infantile and juvenile Alexander disease, but not in adult participants with the disease compared with levels in healthy controls.26
A number of studies have reported that blood GFAP levels are elevated in individuals with brain tumors.27-34 Some studies have found blood GFAP levels to be higher in participants with glioblastoma multiforme (GBM) than in healthy control participants, patients with other non-glial primary tumors and patients with brain metastasis.27-30 In patients with GBM, blood GFAP concentration correlated with preoperative tumor volume,27,28,30,33,34 volume of necrosis27,34 and GFAP expression levels in tumor tissue.27-34 In one study, individuals with systemic metastasis of myxopapillary ependymoma, a brain tumor with high GFAP expression, had very high blood GFAP concentrations compared with those in healthy controls.32