The FDA-approved concussion blood test isn’t ready for prime time

As an emergency medicine physician, a sports medicine physician who has spent countless hours on the sideline, and a concussion researcher, I spent a few minutes on Valentine’s Day reading with great interest the FDA release about a concussion biomarker. Currently, the diagnosis of a concussion is a timely, complicated task, taking into account both subjective historical elements and objective findings from the physical exam. The idea that a blood test could diagnose a concussion would be a game-changer. Unfortunately, after reading the release and the corresponding studies, we have yet to reach the goal line.

The blood test released by San Diego based biotechnology company Banyan Biomarkers looks for serum levels of UCH-L1 (ubiquitin carboxy-terminal hydrolase L1) and GFAP (Glial Fibrillary Acidic Protein).  UCH-L1 is a protein that is specific to neurons, the neuroendocrine system, and the testis/ovaries. GFAP is a structural protein found all over the central nervous system, along with kidneys, and the testis. The newly approved blood test can detect these proteins in the blood, and reportedly these protein concentrations rise within 20 minutes of a head injury.  Interestingly, other studies have found that GFAP and UHC-L1 cannot distinguish orthopedic trauma from head injury, especially acutely.

Since the public, health care providers, and sporting agencies are starving for an objective biomarker to help diagnose concussions, this test was fast-tracked through the FDA, under the Breakthrough Devices Program.  However, there are a variety of reasons why these are not ready for immediate institution at your neighborhood emergency departments.

First, the study endpoint was not the diagnosis of concussion, which is elusive and for which health care providers would appreciate an objective biomarker. The endpoint was a negative CT scan.  So, in essence, the test is to predict who is going to have a negative CT scan of the head.  For almost 20 years now, validated decision rules such as the New Orleans Criteria and the Canadian CT Head Rule for adults as well as PECARN and CATCH and CHALICE rules for kids, have existed to help clinicians decide who needs a CT scan, to help predict who would need brain surgery, and to help limit the radiation exposure from a CT scan to patients.

Subjects were considered to have a mild Traumatic Brain Injury (not clear if this is how they define concussion since the patients were not followed) if they had an initial Glasgow Coma Scale (GCS) > 13 and met one or more of the following criteria: loss of consciousness (LOC), posttraumatic amnesia, or confusion. Since only 10% of concussions experience a LOC, this disregards a lot of people. And I would submit, if someone came to the ED with any of these criteria, they would be diagnosed with a concussion, and we wouldn’t need a blood test.

Practically speaking, the result of this test takes 3 to 4 hours to become available. This would mean that the already crowded emergency departments would now be holding patients for an additional 3 to 4 hours as healthcare providers await the results of a test to tell them if their patient needs a CT scan.  Of course, if the patient did need a CT scan, the patient could have irreversible brain damage in the time it takes for the results to arrive. As a healthcare provider, I truly hope that my colleagues in the ED continue to rely on the Head CT rules that we were taught and do not let a blood test decide which patients to scan.

Furthermore, the authors suggest that a negative CT scan would indicate a concussion.  Any soccer mom, coach, and hockey dad knows, just because Johnny hit his head and is transiently confused does not mean he has a concussion. This test implies differently.

Since the FDA announcement, I have already had patients ask me to draw this blood test, that is by the way not readily available, to help diagnose their child with a concussion.  All this test will tell me is that their child is not bleeding in their brain. While this is a step in the right direction, we are still a long way from a blood test to diagnose a concussion.

Neha Raukar is an emergency medicine physician.

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