A new blood test approved by the Food and Drug Administration is being characterised by the agency and news reports as a way to detect concussion. But a University at Buffalo, USA, expert on concussion says those reports are misleading.
“Calling this blood test a concussion blood test is a misnomer,” said John Leddy, clinical professor in the Department of Orthopaedics and medical director of the University of Buffalo Concussion Management Clinic. “This blood test does not provide a way to confirm or rule out a concussion,” he continued.
If patients think the blood test can diagnose concussion, a negative result on the test may lead them to think they didn’t have a concussion.
“What the patient might hear is that they don’t have a concussion when in fact they do,” he added.
The purpose of the blood test is to determine who should and who should not get a CT scan after a head injury.
According to the FDA press announcement, the blood test measures protein levels in the blood that can help predict which patients may have intracranial lesions visible—by CT scan.”
“This test will help the ER doctor to decide whether or not they should order a CT scan,” Leddy said. That’s worthwhile, he said, 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 here, too, the value of the test may be limited, he said. That is 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?” Leddy asked. “I worked in an ER and I wouldn’t. It could mean the difference between life and death.”
He explained that 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.”
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 explained. “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,” he added, “but rather a group of biomarkers will be required that have clinically useful appearance times in the circulation and specificity for concussion.”