Glossary · Markers and tests
Biomarker
In one sentence
A biomarker is a characteristic that is objectively measured and evaluated as an indicator of normal biological processes, disease processes or responses to a therapeutic intervention. It may be a molecule, a genetic variant or an imaging finding.
Also known as: biomarkers · biological marker · biomarcador
What is a biomarker?
The most widely cited definition comes from the NIH Biomarkers Definitions Working Group, published in Clinical Pharmacology & Therapeutics in 2001: a characteristic objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes or pharmacological responses to a therapeutic intervention. The key idea is that a biomarker stands in for something that cannot be observed directly.
Biomarkers come in many forms: a protein in blood (troponin) or stool (faecal calprotectin), a metabolite, a mutation in tumour DNA, blood pressure or a radiological image.
Types of biomarker
The BEST glossary (Biomarkers, EndpointS, and other Tools), produced jointly by the FDA and the NIH, classifies them by use:
- Susceptibility or risk: estimate the likelihood of developing a disease (for example, BRCA1 variants).
- Diagnostic: detect or confirm a disease or a subtype.
- Monitoring: measured repeatedly to follow the course of a condition.
- Prognostic: estimate the likelihood of a clinical event or progression.
- Predictive: identify who is more likely to benefit from (or be harmed by) a treatment, such as HER2 status and trastuzumab.
- Pharmacodynamic or response and safety biomarkers.
How a biomarker is validated
For a biomarker to be useful in practice, a link with disease in one study is not enough. Three levels are needed:
- Analytical validity: the test measures what it claims to measure (precision, reproducibility, limit of detection).
- Clinical validity: the result consistently tracks the clinical state (sensitivity, specificity, predictive values).
- Clinical utility: using it improves decisions or outcomes for patients.
Many candidate biomarkers in research, for instance in metabolomics or microbiota studies, never get past the first levels. Others, such as zonulin measured by immunoassay, are the subject of methodological debate.
Example
An oncologist uses a predictive biomarker to choose treatment: testing for an EGFR mutation, in tissue or by liquid biopsy, shows whether a patient with lung cancer is a candidate for a targeted drug. Repeated over time, the same type of test can act as a monitoring biomarker.
Biomarkers at Xenogene
Several Xenogene tests measure biomarkers with different purposes: calprotectin as a marker of gut inflammation, the short-chain fatty acids in functional metabolomics as a marker of microbial activity, and circulating tumour DNA in VERUM. They can be combined in the integrated profiles. In every case, the result is interpreted by the requesting professional in its clinical context; Xenogene works exclusively with healthcare professionals.
Frequently asked questions
What is the difference between a biomarker and a tumour marker?
A tumour marker is one kind of biomarker, focused on cancer, such as PSA or CEA. Biomarker is the umbrella term and also covers markers of inflammation, organ function, genetics or drug response.
Does an abnormal biomarker mean I have a disease?
Not necessarily. Many biomarkers can shift for benign reasons, because of medication or because of differences between laboratories. Their meaning depends on the test, the cut-off and the clinical context, and should be interpreted by a healthcare professional.
What types of biomarkers are there?
The FDA-NIH BEST glossary groups them by use: susceptibility or risk, diagnostic, monitoring, prognostic, predictive, pharmacodynamic or response, and safety biomarkers. The same biomarker can serve more than one purpose.
Related terms
- Faecal calprotectin
Faecal calprotectin is a neutrophil protein measured in stool as a marker of inflammation of the intestinal lining. It helps distinguish inflammatory bowel disease from functional disorders such as irritable bowel syndrome.
- Liquid biopsy
A liquid biopsy is the analysis of tumour-derived material, mainly circulating tumour DNA (ctDNA), in a body fluid such as blood. It allows genetic changes in a cancer to be studied without a tissue biopsy.
- Metabolomics
Metabolomics is the large-scale study of metabolites — the small molecules produced by the activity of cells and microorganisms — in a biological sample such as blood, urine or stool. It reflects what is happening in a system at a given moment.
- Zonulin
Zonulin is a human protein, identified as prehaptoglobin-2, that reversibly regulates tight junctions in the intestinal lining. It has been proposed as a marker of intestinal permeability.
Educational content for healthcare professionals and the general public. It does not replace assessment by a healthcare professional: ordering and interpreting any test is the responsibility of the requesting clinician.
Updated on