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FDA Approves Use of Blood Samples as Evidence to Support Alleged Diagnosis of Mild Traumatic Brain Injury

Key Takeaways

  • The Food and Drug Administration has authorized the marketing of a blood test to evaluate a mild traumatic brain injury (TBI) in adults

  • These tests must generally be given within 1-5 days of the injury that is said to produce mild TBI

  • Early prehospital and in-hospital blood levels of certain biomarkers can rule out traumatic intracranial lesions following mild TBI

  • Recent studies have found that valid conclusions cannot be drawn on the diagnostic accuracy of glial fibrillary acidic protein

Since 2018, the Food and Drug Administration (FDA) has permitted the marketing of blood tests to evaluate mild traumatic brain injury (TBI), commonly referred to as concussions. These tests help health care professionals determine the need for CT scans and prevent unnecessary neuroimaging and associated radiation exposure. The tests measure levels of proteins, including glial fibrillary acidic protein (GFAP), released from the brain into blood within 12 hours of injury.

An independent study by Danish research scientists, conducted in 2021, found that levels of S100B proteins safely rule out traumatic intracranial lesions in adult patients with mild TBI. That same study found that GFAP concentrations were only detected in 1% of pre-hospital and 1.6% of in-hospital samples. Thus, the sample size of this protein was deemed too small for diagnostic purposes.


The FDA continues to study TBI. It’s current guidance, issued in the spring of 2021, states that “none of the medical devices cleared or approved by FDA are intended to be used alone without the judgment of a health care provider trained to diagnose and treat TBI. The FDA has not cleared or approved any medical products that are intended to diagnose or treat TBI alone without other diagnostic tests or treatments managed by a health care provider.”


Blood tests may, someday, gain wide use in assessing the severity of mild TBI. However, the assay must be performed at the time of injury―not months or years later. One still requires a proper differential diagnosis and neuropsychological testing to confirm the existence and severity of the condition.

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