The U.S. Food and Drug Administration has recently approved a new blood test that can help emergency room doctors determine whether to order a CT scan for people with head injuries. However, there is some misinformation going around about the test -- some even promulgated by the FDA. Some news and agency reports have said that the new test can detect concussions -- and that is not true.
"This blood test does not provide a way to confirm or rule out a concussion," says a clinical professor at the University of Buffalo and medical director of the UB Concussion Management Clinic and a physician with UBMD Orthopaedics and Sports Medicine.
It is crucial that patients understand that the test does not detect concussions so that they don't misinterpret a negative result as meaning they don't have a concussion. You could have a concussion with a negative result on the test.
What the test does, according to the FDA, is measure certain protein levels in the blood that "can help predict which patients may have intracranial lesions visible by CT scan." Results are back within three to four hours.
With such a long wait, some ER doctors may choose to order a CT scan for many patients with head injuries. However, there is at least one big risk associated with CT scans: radiation. "You never want to expose someone to radiation, especially a child, who does not need it," says the UB professor.
He adds that there are already good clinical rules to help doctors make the decision about which patients need a CT scan. For example, patients with signs of bleeding in the brain, such as a worsening headache, vomiting, lethargy or seizures, should probably have the CT scan. Doctors may not need the new test to determine that. However, it is a good option when people appear to need the CT scan but who are at higher risk from radiation exposure.
There may never be a single test that can detect concussions, the professor says. Concussions do cause various proteins to appear in the bloodstream, but they arrive at different times. One could be present six hours after the injury but could be gone within 48 hours. Another wouldn't be detectible at six hours but could be at 48.
A blood test for concussions would probably require testing for a group of different biomarkers that appear in the blood at different, clinically useful times.
Still, while this new test will not confirm or rule out concussions, it may be useful in detecting traumatic brain injuries without resorting to high-radiation tests like CT scans.