Blood test may obviate need for head CTs in brain trauma evaluation
SAN DIEGO – A biomarker test based on the presence of two proteins in the blood appears to be suitable for ruling out significant intracranial injuries in patients with a history of mild traumatic brain injury (TBI) without the need for a CT head scan, according to data presented at the annual meeting of the American College of Emergency Physicians.
Ted Bosworth/MDedge News
Dr. Jeffrey Bazarian
according to Jeffrey J. Bazarian, MD, professor of emergency medicine, University of Rochester (New York).
In the ALERT-TBI study, which evaluated the biomarker test, 1,959 patients with suspected TBI at 22 participating EDs in the United States and Europe were enrolled and available for analysis. All had mild TBI as defined as a Glasgow Coma Scale (GCS) score of 13-15.
The treating ED physician’s decision to order a head CT scan was the major criterion for study entry. All enrolled patients had their blood drawn within 12 hours in order to quantify two biomarkers, C-terminal hydrolase-L1 (UCH-L1) and glial fibrillary acidic protein (GFAP).
The biomarker test for TBI was negative when the UCH-L1 value was less than 327 pg/mL and the GFAP was less than 22 pg/mL; the test was positive if either value was at this threshold or higher. To evaluate the sensitivity and specificity of this dual-biomarker test, results were correlated with head CT scans read by two neurologists blinded to the biomarker values.
The mean age of the study population was 48.8 years and slightly more than half were male. About half of the suspected TBI in these patients was attributed to falls and about one third to motor vehicle accidents.
Typical of TBI with GCS scores in the mild range, only 6% of the patients had a positive CT head scan. Of the 125 positive CT scans, the most common injury detected on CT scan was subarachnoid hemorrhage followed by subdural hematoma.
Of the 671 negative biomarker tests, 668 had normal head CT scans. Of the three false positives, one included a cavernous malformation that may have been present prior to the TBI. The others were a small subarachnoid hemorrhage and a small subdural hematoma. Overall the negative predictive value was 99.6% and the sensitivity was 97.6%.
Although the biomarker specificity was only 36% with an even-lower positive predictive value, the goal of the test was to rule out significant TBI to avoid the need for CT scan. On this basis, the biomarker test, which is being developed under the proprietary name Banyan BTI, appears to be promising. The data, according to Dr. Bazarian, have been submitted to the Food and Drug Administration.
“Head CT scans are the current standard for evaluating intracranial injuries after TBI, but they are overused, based on the high proportion that do not show an injury,” said Dr. Bazarian. Although he does not know the disposition of the FDA application, he said, based on these data, “I would definitely be using this test if it were available.”
