This article focuses on research conducted as part of the TRACK-TBI multicenter study examining the causes and outcomes of TBIs of all severities.
Diagnosing a mild traumatic brain injury (mTBI) is not always straightforward. Although many patients who are admitted to the emergency department for mTBI will receive brain imaging scans, such as computerized tomography (CT), these imaging tools may or may not reveal evidence of brain damage—even when an mTBI did occur. Another form of imaging called magnetic resonance imaging (MRI) provides more detail than CT scans, but MRI equipment is costly to use and still may fail to show small brain abnormalities associated with injury. Clinicians should therefore understand that, while CT and MRI scans might detect the presence of a milder brain injury in some cases, they cannot use it as a tool to rule out brain injury entirely.
Given the limitations of brain imaging techniques, health care providers have searched for more definitive ways to diagnose mTBI. One alternative is to screen for biomarkers, molecules found in the blood that can indicate the presence of a certain condition. Clinicians commonly use biomarkers to diagnose diseases, disorders, and injuries. Recently, researchers have begun to identify biomarkers that specifically indicate the presence of mTBI, even when imaging scans fail to show evidence of injury.
In this study, researchers sought to determine whether the presence of a biomarker called glial fibrillary acidic protein (GFAP) could be used to help confirm the results of imaging techniques such as CT and MRI scans if taken within 24 hours of an mTBI. They chose to investigate GFAP because this protein is found in the brain, and prior studies of patients with severe TBI have found that GFAP levels increase in direct proportion to brain injury severity. Consequently, the researchers wondered if GFAP can also indicate the presence of milder brain injuries.
The research team recruited patients who presented to the emergency room for head injury and who were diagnosed with mTBI using gold-standard clinical criteria for brain injury. Despite their mTBI diagnoses, all patients had normal CT scans, and some had normal MRI scans. Because the MRI results showed more variation, researchers attempted to use GFAP to confirm the findings of each patient’s MRI scan. To determine if GFAP is only present in the blood of TBI patients, the researchers also examined GFAP levels in a group of patients who had either experienced a non-head injury or were not injured at all.
The reseachers found that GFAP concentration was higher in mTBI patients who had abnormal MRI findings than those who had normal MRI findings. They also found that these results were dose-dependent: the lower the concentration of GFAP in the blood, the more likely they were to find negative MRI findings. In other words, low concentrations of GFAP correlated with normal (negative) MRI findings, and higher concentrations of GFAP correlated with abnormal (positive) MRI findings.
The authors of the study concluded that GFAP could be used to confirm MRI results. Importantly, these results indicate that clinicians can effectively use GFAP to rule out the possibility of false-negative MRI results. When clinicians are certain that a patient does or does not have TBI, they are better able to make informed decisions about patients’ treatment needs during the recovery period. Biomarker-based diagnostic techniques also reduce costs for patients, as blood tests are far less expensive than MRI or CT scans.
While the diagnostic efficacy of biomarkers still demands further research, the first step is to show that they are, at a minimum, as effective as standard diagnostic techniques. The findings of these studies indicate that GFAP is an effective, cost-saving method diagnostic method that, in some cases, may provide more nuanced data than brain imaging scans.