Abstract
The official definition of a biomarker is “A characteristic that is objectively measured and evaluated as an indicator of healthy biological processes, pathological processes, or pharmacological responses to therapeutic intervention”, so the overall idea is to move from clinical judgment to more objective measurements. I will start by illustrating the issues based on well known biomarkers, such as weight, body temperature, blood pressure and blood glucose. Then follows an overview of the potential purposes of biomarkers. For obtaining acceptance of a new biomarker (both regulatory acceptance as well as general acceptance), the biomarker must be both validated (proven to measure what it intends to measure, in the technical sense) and qualified (proven to measure something that is clinically relevant). The clinical studies needed for qualification will be discussed.