First things first: There is currently no blood test that conclusively determines if a person has sustained a concussion or not. This is a distinction clinicians have been quick to emphasize following the announcement by the Food and Drug Administration in February that it approved the first-of-its-kind “brain trauma assessment test.”
The FDA noted that a brain trauma assessment test by its definition is “used to detect and measure brain injury biomarkers in human specimens.” The Banyan BTI (which stands for “Brain Trauma Indicator”) blood test it approved, which was developed by San Diego-based Banyan Biomarkers, measures the blood levels of two proteins found in brain tissue, known as UCH-L1 and GFAP. Depending on the levels of these proteins released in the blood, a positive test indicates a patient likely has intracranial lesions, or bleeding in the brain, that would be visible in a CT scan. “The measurements aid in the evaluation of patients with suspected mild traumatic brain injury in conjunction with other clinical information to assist in determining the need for head imaging per current standard of care,” the FDA notes in an authorization letter to the company regarding the approval of the blood test.
The agency added in a press release that research findings “indicate that the test can reliably predict the absence of intracranial lesions and that health care professionals can incorporate this tool into the standard of care for patients to rule out the need for a CT scan in at least one-third of patients” suspected of having mild TBI.” This can prevent unnecessary radiation exposure for patients, and also save them and the health care system money on unneeded scans, experts says.
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However, while the FDA and Banyan Biomarkers have noted the test’s specific indication for use, clinicians say amid all the excitement surrounding the test in subsequent media coverage, it’s been made to seem as if the test is more broadly applicable in diagnosing concussion. Namely, experts point out that the vast majority of people with a concussion do not experience the type of bleeding that would show up on a brain scan. “What percentage have blood on the brain? It’s less than 5 percent,” says William Barr, director of the neuropsychology division at the NYU Langone Health’s Concussion Center in New York City. For the rest, a negative test could rule out the need for a CT scan, say, when an individual comes into the emergency room suffering from symptoms of a concussion. But he notes that it wouldn’t otherwise help in determining whether or not a person had in fact sustained a concussion.
“What this test does is if the test is negative, then it’s felt that there’s no reason to get a CAT scan,” Dr. Thomas Watanabe, clinical director of the Drucker Brain Injury Center at MossRehab in Elkins Park, Pennsylvania. “So that saves everybody money and patients from unnecessary risk of radiation. But it really hasn’t helped the clinician make a decision of whether that patient has a concussion or not.”
That’s important to note, experts say, since a clinical assessment of the patient is key in making that determination. “As of right now, I think the way to diagnose concussion hasn’t changed even with this test,” Watanabe says. “The diagnosis is still based more on a neurologic exam and asking about symptoms that might be related to a concussion.”
It’s not yet clear the extent to which the blood test will be used going forward, but experts say it may be helpful in clarifying if a patient needs a brain scan, when that’s not already clear from a clinical assessment. Imaging allows clinicians to check for bleeding caused by a traumatic brain injury — which can range from mild to deadly. “If the bleeding doesn’t stop, it can cause pressure on the brain and it could be potentially life-threatening,” Barr says. But he reiterates that the vast majority of concussions do not result in positive MRIs or CAT scans — “the concussion is a functional injury, meaning that brain function is temporarily disrupted,” Barr says. “It’s not thought to have any gross pathological consequences — so you don’t see the brain change shape or anything like that with a single concussion.”
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Experts say that makes it all the more important that doctors get clear information about the individual’s symptoms and what’s happened when it’s believed a person might have sustained a concussion — whether it may have occurred on the battlefield, a playing field or on the road during a car accident. “When somebody has a concussion [and] they go to the emergency room, they have to be in a position to share with the clinician all the symptoms that they’re experiencing,” Barr says. That includes providing information on what the injury was like, in terms of the loss of consciousness and any amnesia associated with it. A diagnosis typically is made based on signs and symptoms a patient describes as well as those they’re exhibiting, such as headache, confusion, slurred speech and appearing to be dazed.
But for some, the concussion symptoms themselves can make it hard to accurately relay such details. “As one might imagine, if you lose consciousness, you don’t know what happened,” Barr points out. “And then some patients have amnesia for the period of time leading up to the accident.” That’s why it can be very helpful, experts say, to have a family member or another advocate who’s aware of the patient’s health history and the circumstances surrounding the potential concussion (if known).
For patients who undergo the blood test to assess the need for CT imaging, the risks of the test are limited mainly to false positive or negative results — and study data the FDA evaluated found it to be reliable, as test results corresponded closely with the likelihood of a brain imaging revealing bleeding. The Banyan BTI “was able to predict the presence of intracranial lesions on a CT scan 97.5 percent of the time and those who did not have intracranial lesions on a CT scan 99.6 percent of the time,” the FDA notes.
But it’s key that the results are properly interpreted and not misconstrued by clinicians or patients, experts say. “I think one of the most important things is that when the test is negative — meaning that there’s no findings on it — it doesn’t mean you didn’t have a concussion,” Barr stresses.
Unfortunately, it’s not always clear if a person sustained a traumatic brain injury, and doctors say that can be unsettling not to be able to determine this more definitively in some patients. “We all struggle with these borderline cases,” Watanabe says.
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That’s what makes the idea of a test that could one day make such a conclusive determination so alluring. “It would be beautiful if we had a test — whether it’s imaging or blood — that would say you have a concussion or not. But I don’t see that we’re very close to that,” Watanabe says. “Concussions are so subtle, I’m not sure that we’ll really ever quite get there.”
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Should You Get a Blood Test Before Being Scanned for a Possible Concussion? originally appeared on usnews.com
