Hero and sidekick. Peanut butter and jelly. Thunder and lightning. Glial fibrillary acidic protein (GFAP) and ubiquitin carboxyl-terminal hydrolase L1 (UCH-L1). It’s a mouthful of a word pair, but it’s a unique one that opens the door to understanding concussion, sometimes called a mild traumatic brain injury or mTBI. From bumps to blows to jolts to the head, GFAP and UCH-L1 are a reliable pair of biomarkers released into the bloodstream after a brain injury. From a broad perspective, biomarkers are characteristics of the body that are measurable, like blood pressure or amounts of a protein in the blood, and they help assess our health. Let's take a closer look at how this invisible couple impacts concussion assessment. A Biomarkers Analogy If you show up to the emergency room, hand on your heart and complaining of chest pain, you're likely getting a blood test. The test you receive will look at the levels for a protein called Troponin-I, which appears more in the blood after a heart attack. Healthcare professionals have had blood tests for the heart, liver and kidneys for some time, but not one for the brain. When looked at together, the GFAP and UCH-L1 biomarkers open the window to understanding concussions. Exploring the use of biomarkers to better understand what is going on in the body began with the link between troponin and suspected heart attack. Although it took years for troponin to be officially adopted as the standard of care, it did occur in 2007 – and the same could happen for GFAP and UCH-L1 for traumatic brain injuries in the future.