This is often the case following mild traumatic brain injury, when symptoms are subtle and scans of the brain have no obvious abnormalities. Even if the computed tomography (CT) scans do not show clear evidence of damage, patients may have headaches, dizziness, or concentration and memory trouble. New research indicates that blood biomarkers may allow physicians to diagnose some of these overlooked injuries.
The researchers looked at glial fibrillary acidic protein, or GFAP, and ubiquitin C-terminal hydrolase-L1, or UCH-L1, both of which are found in brain cells and can be released into the blood following trauma.
GFAP, which is produced by astrocytes (these are cells that help protect and support nerve cells), can increase fairly rapidly after a brain injury and might be able to reflect damage to the tissue.
UCH-L1 is released from neurons and can also make its way into the bloodstream after trauma. While the markers are both indicative of injury, the researchers found that each was not quite as effective as the other at picking up abnormalities that the initial CT scans didn’t show.
GFAP outperformed UCH-L1 on the test, mostly when investigators looked for whether an injury wasn’t picked up on a CT scan but could be seen on magnetic resonance imaging (MRI). So the right marker should be used when doctors are searching for injuries that aren’t evident on initial scans.
The study used data from the Transforming Research and Clinical Knowledge in Traumatic Brain Injury, or TRACK-TBI, study. Researchers studied 1,718 patients who had mild traumatic brain injuries with Glasgow Coma Scale scores of 13-15, which people see as a mild injury.
Of those, 633 had injuries detected on CT scans. Of the remaining 1,085 people whose CT scan did not show any damage, 608 had an MRI about two weeks after the injury. The MRI scan found signs of injury in 154 of those patients, about one quarter of those who had the extra test.
Next, the researchers looked at whether blood biomarker levels within 24 hours of injury could differentiate patients with visible abnormalities from those without any evidence of injury on brain imaging.
GFAP outperformed UCH-L1 in detecting CT visible injury, as well as MRI abnormalities in patients with negative head CTs. These results may aid clinicians in recognizing patients who require more intensive clinical monitoring, additional imaging, and dedicated follow-up.
CT scans are still an essential first line for evaluation of suspected brain trauma because they can rapidly look for life-threatening bleeding.
Blood tests might also offer extra clues for doctors to judge if further investigation is needed. Instead of relying solely on symptoms and imaging results from the start, clinicians might be able to pair biomarker levels with the patient’s medical background, neurological examination, and the nature of the trauma.
The University of Pittsburgh group also reported on a different whole blood-testing platform for use in emergency departments. In a study of 970 patients, the combined GFAP and UCH-L1 test demonstrated a sensitivity of 96.5% and a negative predictive value of 96.5% for intracranial injury on CT.
