The FDA recently gave clearance for a new rapid blood test for mild traumatic brain injuries, or concussions. In media articles this new test has been touted as “game changing” for evaluating concussions. But can the test really diagnose a concussion on the sidelines? I have had a few questions about it, so I want to explain what this new test really means for concussions in athletes.
The new test, from Abbot Laboratories, measures specific proteins in the blood that can be elevated in traumatic brain injuries. Right now, the primary use of this test is in the emergency room to determine whether or not a patient should get a CT scan. This is important because every CT scan exposes the patient to radiation, which can increase the risk of developing cancer. Damage to the brain occurs with a concussion, but traditional medical imaging doesn’t show that damage or any bleeding in the brain in the vast majority of cases. We don’t want to subject patients to radiation when the scan is likely to yield no meaningful findings that would affect patient care. Of course, there are rare occasions where bleeding is present, and the consequences of missing it can be dire.
That’s where this test comes in. The patient undergoes a simple blood draw. A hand-held machine will then process the plasma in the blood, looking for specific proteins that would raise concern. The results are ready in less than 15 minutes. If the protein levels in the blood are normal, the patient likely does not have a brain bleed, and there is no need for a CT scan. As a bonus, it will save patients time waiting in the ER, and a blood test costs substantially less money than a CT scan.
What does this mean for concussions in athletes? At this point, not much. The test is only approved for individuals ages 18 or older. There is some evidence that the protein levels in the blood may be different in children following concussions or other traumatic injury compared to adults. The developing brain is undergoing a variety of processes and changes, and it doesn’t always react the same way as the adult brain to environmental factors, such as a head impact. At the youth and high school level, it would be difficult to do a blood draw on the sideline. The test also requires the plasma to be separated from the blood before being tested in the handheld machine, which requires special equipment. As a result, this test is really only useful in the hospital (and potentially clinic) setting to rule out the need for a CT scan. It isn’t a tool that could be used to diagnose a sports-related concussion on the sideline.
It’s also important to know that we have a lot to learn about these blood biomarkers in the brain when it comes to diagnosing concussions in sports. At this point, having normal levels of these proteins in the blood does not necessarily mean a patient doesn’t have a concussion. They simply may not have enough damage to the brain to cause substantially increased levels of these proteins in the blood. Research has shown that these markers tend to be particularly high in patients who lost consciousness or have post-traumatic amnesia, but only about ten percent of concussions result in a loss of consciousness, and amnesia is not a common symptom either. It is critical that clinicians consider the entire clinical picture, including the patients symptoms and other potential signs of a concussion.
Despite these current limitations, there is great promise for a sideline concussion blood test in the future. Right now we have to rely primarily on the patient disclosing their symptoms, and many athletes hide their concussion symptoms in order to stay in the game. Research is investigating the proteins examined in this test as well as other proteins in the blood that might indicate that an athlete has a concussion. It is very likely that athletic trainers and team doctors will someday be able to use a finger-prick blood test with a handheld sideline device to diagnose a concussion in minutes, or even seconds. Other research is looking into saliva tests to diagnose concussions.
This biomarker research could lead to advancements beyond simply diagnosing concussions. Studies have shown that blood protein levels shortly after the injury may predict who will have a prolonged recovery. Another challenging aspect of concussion management is knowing when the athlete is ready to return to play. Like diagnosing a concussion, readiness to return to play is typically determined based on the athlete’s symptoms. An athlete could claim their symptoms have resolved before they really have so they can return to play as soon as possible. Certain proteins in the blood may remain elevated as the brain is healing, and following the levels of these proteins over the days or weeks following the concussion could give us insight as to when the brain has healed and it is safe for the athlete to return to play.
This new test is a step in the right direction, and it has the potential to have great benefit in the emergency room. While the science has come a long way, it just hasn’t hit the finish line yet. We have more work to do before we can use this type of test becomes a regular part of a sideline concussion evaluation.