The search for blood biomarkers useful in the management of traumatic brain injury (TBI) has been one of the holy grails of the clinical neurosciences for several decades. Biomarkers are molecules that can be measured in accessible biological fluids that reflect physiological, pharmacological, or disease processes and can suggest the etiology of, susceptibility to, activity levels of, or progress of a disease. According to the US Food and Drug Administration, biomarkers fall into 3 categories, which are not mutually exclusive: prognostic, predictive, and pharmacodynamic.1 Prognostic biomarkers are baseline measurements that categorize patients by degree of risk for disease progression and inform about the natural history of the disorder. Predictive biomarkers are baseline characteristics that categorize patients by their likelihood of response to a particular treatment. Finally, pharmacodynamic biomarkers are dynamic measurements that show that biological response has occurred in a patient after a therapeutic intervention. Biomarkers have historically been critical to progress in a broad range of clinical conditions. Diagnostic and therapeutic advances in fields as disparate as cardiology and oncology have relied on the ability to measure biomarkers that are reliable indicators of the underlying pathology.
Gatson J, Diaz-Arrastia R. Tau as a Biomarker of Concussion. JAMA Neurol. 2014;71(6):677-678. doi:10.1001/jamaneurol.2014.443