Biomarkers range from a simple molecule to a complex substance; from basics like blood pressure and pulse to a more composite lab tests of various body parts including blood and tissues. However, biomarkers are merely a medical sign like any other. It is one of the most objective and measurable clinical signs a modern laboratory can have.
A bio marker or biological marker, are defined as an indicator of a biological state of a living body. It is a characteristic that is measured and evaluated as an indicator of normal biological processes.
Biomarker identification based on hypothesis approach uses mechanistic realization of the disease processes. In contrast, discovery based methods have emphasized on recognizing changes in the relative abundance or presence of molecular species (McDermott et al., 2013).