A biomarker, or biological marker, is in general a substance used as an indicator of a biological state. It is a characteristic that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention. It is used in many scientific fields.
In medicine, a biomarker can be a substance
that is introduced into an organism as a means to examine organ function
or other aspects of health. For example, rubidium chloride is used as a
radioactive isotope to evaluate perfusion of heart muscle.
It can also be a substance whose detection indicates a
particular disease state, for example, the presence of an antibody may
indicate an infection. More specifically, a biomarker indicates a change
in expression or state of a protein that correlates with the risk or
progression of a disease, or with the susceptibility of the disease to a
given treatment.
A biomarker can also be used to indicate exposure to various
environmental substances in epidemiology and toxicology. In these cases,
the biomarker may be the external substance itself (e.g. asbestos
particles or NNK from tobacco), or a variant of the external substance
processed by the body (a metabolite).
In cell biology, a biomarker is a molecule that allows for the detection
and isolation of a particular cell type (for example, the protein Oct-4
is used as a biomarker to identify embryonic stem cells).
In genetics, a biomarker (identified as genetic marker) is a DNA sequence
that causes disease or is associated with susceptibility to disease.
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"Biomarker"
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