Blood test in ER can predict prognosis in TBI

By John Murphy, MDLinx
Published January 5, 2016

Key Takeaways

A blood test for brain-derived neurotrophic factor (BDNF) could help emergency department doctors quickly diagnose a patient’s traumatic brain injury (TBI) to gauge its severity and also predict how well the patient will recover.

This discovery, published in the Journal of Neurotrauma, could help identify patients who might benefit from extra therapy or experimental treatments.

“Compared to other proteins that have been measured in traumatic brain injury, BDNF does a much better job of predicting outcomes,” said study author Frederick Korley, MD, PhD, assistant professor of emergency medicine at the Johns Hopkins University School of Medicine.

Such a predictor would be useful because most ED departments rely only on CT scans and patients’ symptoms to determine whether to send patients home or take extra precautions. But CT scans can only detect bleeding in the brain, not damage to brain cells, which can happen without bleeding. 

“A typical situation is that someone comes to the emergency department with a suspected TBI, we get a CT scan, and if the scan shows no bleeding, we send the patient home,” Dr. Korley said. “However, these patients go home and continue having headaches, difficulty concentrating, and memory problems, and they can’t figure out why they are having these symptoms after doctors told them everything was fine.”

So, Dr. Korley and collaborators at centers around the world wanted to determine if a blood test could better predict which patients will have ongoing brain injury-related problems. To do so, they evaluated blood samples in more than 300 patients with TBI and in 150 patients without TBI, and measured the levels of three proteins that they suspected play a role in brain cell activity. They followed patients for 6 months.

They found that lower levels of one protein, BDNF, taken within 24 hours of a head injury, could predict the severity of TBI and how the patient would fare. While people without TBI averaged 60 ng/ml of BDNF in their bloodstreams, patients with TBI had less than one-third of that amount, less than 20 ng/ml on average. Patients with the most severe TBIs had even lower levels, around 4 ng/ml.

Patients with high levels of BDNF had mostly recovered from their injuries 6 months later, the researchers found. But patients with the lowest levels of BDNF still had lingering symptoms at follow-up. These results suggest that a test for BDNF levels, administered on day-of-injury in the emergency department, could help stratify patients—the lower the BDNF level, the higher the odds of incomplete recovery.

“The advantage of being able to predict prognosis early on is that you can advise patients on what to do, recommend whether they need to take time off work or school, and decide whether they need to follow up with a rehab doctor or neurologist,” Dr. Korley said.

More research is needed to find out why, at a molecular level, brain injuries have lower levels of BDNF in the blood, and whether interventions known to increase BDNF levels—such as exercise and omega-3 fatty acids—could help treat TBIs, Dr. Korley said.

He also wants to know whether changes in BDNF levels over time can be a marker for recovery and if they could be used to determine the effectiveness of an intervention. “We looked at that very first blood sample obtained within 24 hours of an injury,” he said. “But for BDNF to be used as a surrogate outcome, we’ll have to see what happens to BDNF blood levels down the line at 1, 3 or 6 months after the injury.”

Dr. Korley and his collaborators have already started collecting data for those prospective studies, he added.

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