Blood Markers Could Determine Necessity of CT With Mild TBI

A blood test may be able to diagnose patients with a concussion or traumatic brain injury (TBI), cutting the need for a head CT, according to a study published Nov. 15, 2014 in the Journal of Neurotrauma. Glial fibrillary acidic protein (GFAP) seems to be a brain-specific marker of trauma and out performed S100β in predicting intracranial lesions on CT, particularly in patients with non-head-related fractures. Lead author Linda Papa, M.D., tells DTET that GFAP, a relatively new marker associated with TBI, is a protein that "spills out" of glial cells in the brain into cerebrospinal fluid and blood with brain injury. By contrast, Papa says S100β (a major low-affinity calcium binding protein in astrocytes) is the most well-studied biomarker for TBI, but is not sufficiently brain-specific and rises in patients with non-head bone injuries. "GFAP is loyal to the brain even in the face of other fractures," says Papa, from Orlando Regional Medical Center and the University of Central Florida. Papa and colleagues assessed the ability of GFAP and S100β to predict the presence of traumatic intracranial lesions on CT scan (n=262 patients) in a convenience sample of adult trauma patients with and without mild or moderate TBI (without 47 percent). Serum samples were obtained within four hours of injury. Samples were analyzed in batches using sandwich enzyme-linked immunosorbent assays. Both GFAP and S100β rapidly appeared in serum post-injury, with levels detectible within an hour of injury. S100β appeared most elevated within the first two hours, while GFAP levels remained steady over four hours. The researchers found that levels of both markers were significantly higher in those with lesions on CTs. But GFAP levels were significantly higher in those with intracranial lesions, while S100β was unable to discriminate between intracranial and extracranial lesions on CT. In the presence of fractures, GFAP had a specificity of 55 percent, compared to 5 percent for S100β. The potential market for a diagnostic test is "large," Papa says with two percent of all emergency room visits due to TBI. Additionally, such a test, if adapted for the point-of care, could be used on the field or locker room in sports settings. Papa says she is currently working with the U.S. Food and Drug Administration and several companies interested in commercializing a TBI test. In addition to reducing the use of CT, especially in young patients, the use of markers may provide a more sensitive diagnosis than can be made on CT, enabling earlier diagnosis and treatment. Several study authors report financial ties to Banyan Biomarkers (Alachua, Fla.), which is working to develop a point-of-care test to diagnose TBI. Takeaway: The use of biomarkers may improve definitive TBI diagnosis and could potentially reduce the need for head CT and associated radiation exposure, particularly in young patients.