Glial Fibrillary Acidic Protein (GFAP) and Ubiquitin Carboxy-terminal Hydrolase L1 (UCH-L1) to Exclude Lesions Linked to Significant Traumatic Brain Injuries

This study is looking for adults aged 18 and over who have recently had a mild head injury. To be potentially included, your head injury must have involved either a hit to the head or face, or a sudden jolt, and your alertness level (measured by something called a Glasgow Coma Scale) should be 13, 14, or 15. You also need to have at least one of these situations: you're over 65 and taking blood thinners for your heart; your alertness level dropped two hours after the injury AND you had alcohol or drugs in your system; your injury happened from a forceful event like being hit by a car or falling from a height; or you can't remember more than 30 minutes before the injury.

For the blood test to be useful for the study, your blood sample needs to be taken within 12 hours of your injury, and your doctor must have already planned for you to have a CT scan as part of your usual care. You also need to be able to understand and sign a consent form to join the study.

You won't be able to join if you don't have health insurance, are under legal protection, or your blood sample is taken more than 12 hours after your injury. You'll also be excluded if your doctor already knows you definitely need a CT scan because of certain other problems, such as if your alertness level is very low (below 13), you have a bleeding disorder, show signs of a skull fracture, have vomited many times, had a seizure after the injury, or have new weakness or numbness. Finally, if it would be difficult for the researchers to follow up with you a week later, you wouldn't be able to participate.

If you decide to take part in this study, you will continue to receive all your usual medical care and treatment in the emergency department, exactly as your doctors would recommend. There will be two extra parts to your participation:

1. **Extra Blood Sample:** When the nurses take blood for your routine tests, they will take a tiny bit more at the same time for the study. This won't involve any extra needle sticks. 2. **Follow-up Phone Call:** About seven days after you leave the hospital, a member of the research team will call you for a brief chat. This call is to check how you are doing and gather a little more information about your recovery.

Your involvement will not change the treatment you receive, and the study will only add these two simple steps to your existing care plan. The total duration of your participation, from the blood test to the follow-up call, will be about seven days.