What Exactly Is a Biomarker?

A biomarker is any measurement that provides information on a patient's specific organ or organ system. A simple blood biomarker test like those used to test heart attack or liver function is greatly needed for brain injury.

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A biomarker is any measurement that will provide information on the organic status of an individual or an individual system or organs within a patient. It doesn't have to be a biomarker in the blood. It can be an image, a CT scan. It can be a functional assessment. Any entity that provides that information becomes a biomarker. Currently, the biomarkers used in a traumatic brain injury are functional assessments that are called the Glasgow Coma Scale. It's just whether you're obtunded, your name, where you are, or commonly a CT scan. The problems with those are the GCS was never intended to be used to diagnose TBI, especially mild TBI. It doesn't discriminate whether you're drunk or had a concussion, and CT scans are relatively insensitive. You can have brain damage that you can detect with more sensitive imaging like magnetic resonance imaging, and it won't appear on a CT. And in fact, MRI, or magnetic resonance imaging, is not available, not used, so it's not standard care. People have recognized the need to have a simple blood test, and in fact, these blood biomarkers are used widely in medicine now. They always have been. We take glucose measurements, of course, for diabetes, a variety of markers tracking liver function are routinely measured. In acute medical environments that are life threatening, the most widely used biomarker is a protein called troponin. When you have a heart attack or a myocardial infarction, and if troponin is elevated, it provides more information on increased probability that you had a heart attack. Well, the brain is an organ that needs a biomarker like that. The idea is to measure proteins or fragments of proteins that indicate injury, just like troponin is a protein that's found in the muscles, in heart muscles, and it's released when these heart muscles are damaged because they're not getting enough blood. The brain releases other proteins that are damaged when the brain is injured. If you can measure those proteins in the blood, you have a relatively straightforward, non-invasive and ideally rapid way of providing that information. How damaged is the brain? The ideal biomarker would be an abundant protein that would be easy to measure in what we call an assay of it that would be released at injury quickly, so you'd know that you'd been injured. It would persist long enough to measure it and would be, of course, specific to the brain and also provide other information about what type of brain cell is injured, whether it's a neuron or other kinds of brain cells called glia that exist in the brain, and even better, what part of the neuron was injured. Was it the cell body? Was it the axon? Was it the synapse that connects to another neuron? That's the kind of information you'd like to have.
Posted on BrainLine April 2, 2013.

Produced by Brian King, Vicky Youcha, and Erica Queen, BrainLine.