In medicine, a biomarker is a measurable state that is useful in diagnosis or prediction of disease. Examples of biomarkers include those that increase the risk of illness, such as an abnormally high level of toxin in the body, and those that indicate existing disease, like an unusual concentration of a particular protein that is associated with a neurological disease. Traditionally, doctors used biomarkers like the presence of blood in the urine, or high blood pressure, as an indication of disease, but new research is ongoing into less obvious biomarkers, such as genetic damage, or problems at the cellular level.
Medical professionals diagnose diseases through the signs of its presence. For example, a person with Parkinson's Disease may have uncontrollable tremors, and be unable to move around efficiently. If scientists can look more closely at the person with the illness, down to the level of the chemicals in his or her body, and the genes that control the individual cells, then subtler signs of the disease should be identifiable.
A biomarker, therefore, can add to the tools a physician has at his or her disposal to recognize disease. A potential advantage of a biomarker is that it may be present, and recognizable to the doctor, before the disease causes serious damage to the person. Earlier detection of illness often makes a condition more easily treated, and more likely to be curable.
Genes can be biomarkers, if they contain mutations which make a particular disease more likely or certain to develop. Examples of biomarker genes include the BRCA1 gene that contributes to the development of some breast cancers, and the gene for Huntington's Disease, a neurological illness that develops only in adulthood. Genetic screening for gene types that scientists have identified and matched up with medical problems may help with early diagnosis and also allow people who carry a defective gene to plan having children without passing the gene on.
Many different chemicals perform some function in the body. The normal levels of these molecules can change if the body is undergoing a stress. When a scientist identifies a certain molecule that alters according to a recognizable disease state, he or she may then be able to create a test for the molecule that can indicate the presence of that illness. Due to the complexity of the human body, accuracy is a problem, as many molecules perform more than one function and can change with different situations. The knack to a useful and accurate biomarker molecule, therefore, is a molecule that makes characteristic changes that accurately reflect disease, or point strongly enough toward a disease to be practical.
As well as signs of disease that are part of the body's natural workings, a biomarker can also be a substance that is not present naturally in the body. The level of an environmental toxin in a person's body, for example, can give a doctor an indication as to how likely the development of a particular disease is for that person. Along with many other biomarkers, toxins may be measurable through samples from the body like blood or urine. More unusual sources of potential biomarkers, which are less invasive or embarrassing than the traditional samples, include tears and spit.
