What is a Biomarker?

The term biomarker is a research shorthand for biological markers.  While whole committees have been struck - such as the 1993 US National Institutes of Health Biomarkers Definitions Working Group  - to help define the term, it is generally used to indicate medical signs which can be objectively and accurately measured outside the patient's body.

The World Health Organization (WHO) defines biomarkers used in environmental risk assessment as "almost any measurement reflecting an interaction between a biological system and a potential hazard, which may be chemical, physical, or biological.

The measured response may be functional and physiological, biochemical at the cellular level, or a molecular interaction."

Examples of biomarkers studied in health science research range from simple to complex, and include:

  • Pulse
  • Blood pressure
  • Blood glucose levels
  • Cortisol levels as an indicator of longevity-threatening stress
  • Ocular pressure in glaucoma patients
  • C-reactive protein as a measure of inflammation
  • Genes derived from blood samples
  • The presence of drugs or their metabolites in blood

Certain genetic indicators such as the SIRT1 gene have been investigated as a measure of the aging process (and therefore the biological age of a subject); these would be considered biomarkers of aging.

In a 2005 paper, Jeffrey Aronson, Chairman of the Editorial Board of the British Journal of Clinical Pharmacology cautions that biomarkers do not always accurately represent the success of a treatment, or progression of disease, and therefore are not always a good "surrogate" indicator of a desired endpoint.


While biomarkers can provide information earlier, more quickly, and more cheaply compared with more complex diagnostic tests, Aronson argues that these measures should only be used to test the effectiveness of a drug protocol, program, or other intervention when the disease and how it develops is itself well-understood.


Aronson JK. Biomarkers and surrogate endpoints. British Journal of Clinical Pharmacology. 2005;59(5):491-494.

Kyle Strimbu and Jorge A. Tavel. "What Are Biomarkers?" Curr Opin HIV AIDS. 2010 Nov; 5(6): 463–466.

WHO International Programme on Chemical Safety Biomarkers and Risk Assessment: Concepts and Principles. 1993.

Continue Reading