Published February 21, 2018
The first blood test to help doctors diagnose traumatic brain injuries has won Food and Drug Administration (FDA) approval, but misconceptions abound about what it can accomplish.
The FDA and news reports are characterizing the test — known as the Banyan Brain Trauma Indicator — as a way to detect concussion.
“Calling this blood test a concussion blood test is a misnomer,” says Leddy, a physician with UBMD Orthopaedics & Sports Medicine. “This blood test does not provide a way to confirm or rule out a concussion.”
If patients think the blood test can diagnose concussion, a negative result on the test may lead them to think they don’t have a concussion.
“What the patient might hear is that they don’t have a concussion when in fact they do,” Leddy says.
The blood test detects two proteins present in brain cells that can leak into the bloodstream following a blow to the head.
By measuring these protein levels in the blood, the test “can help predict which patients may have intracranial lesions visible by CT scan,” according to the FDA.
“This test will help the emergency room doctor to decide whether or not they should order a CT scan,” says Leddy, noting that this is worthwhile because CT scans expose patients to relatively high levels of radiation.
“Of course, you never want to expose someone to radiation, especially a child, who does not need it.”
But again, the value of the test may be limited, Leddy says. That’s because the blood test provides results within three to four hours, longer than it would take to simply order a CT scan.
“Will ER physicians feel comfortable waiting three to four hours for the result before ordering a CT scan if he or she has reason to believe the patient has had a brain bleed?” he asks. “I worked in an ER, and I wouldn’t. It could mean the difference between life and death.”
Leddy says emergency room doctors currently have very good, validated clinical rules about which patients would benefit from a CT scan after a head injury.
“And if a patient doesn’t have signs of a brain bleed, such as lethargy, seizures, worsening headache or vomiting, then they may not need this test,” he adds.
Leddy is cautious about the potential for future diagnostic tests that might be able to detect whether someone has experienced a concussion.
“After a concussion, there are multiple proteins that appear in the blood at different times,” he explains. “One protein may be present six hours after the concussion but will disappear within 48 hours, while another may not be present six hours afterward but will start to emerge within 48 hours.”
“There will probably never be one single biomarker that can reveal if someone has had a concussion,” Leddy adds, “but rather a group of biomarkers will be required that have clinically useful appearance times in the circulation and specificity for concussion.”