biomarkeri

Biomarkeri, or biomarker, is a measurable indicator of a biological state, condition, or process. Biomarkers can reflect normal physiology, disease presence, disease progression, or the effect of treatment. They may be molecules such as proteins or nucleic acids, imaging features, physiological measurements, or other quantifiable traits. Biomarkers are used across research, diagnostics, and clinical care to characterize health status, stratify patients, and monitor responses to interventions.

Biomarkers are commonly grouped by their clinical purpose. Diagnostic biomarkers help determine whether a disease is present. Prognostic biomarkers provide information about likely outcomes independent of treatment. Predictive biomarkers indicate the likelihood of response to a particular therapy. Pharmacodynamic or monitoring biomarkers track biological responses to a treatment over time, guiding dosing and duration. In trials, surrogate endpoints act as stand-ins for clinical outcomes when direct measurement would be impractical. Examples include C-reactive protein as an inflammation marker, PSA for prostate cancer risk, HbA1c for long-term diabetes control, BRCA mutations for cancer risk, and HER2 expression guiding trastuzumab therapy.

Discovery and use of biomarkers rely on methods such as immunoassays, polymerase chain reaction, sequencing, proteomics, metabolomics, and advanced imaging. Validation requires demonstrating analytical validity (reliable measurement), clinical validity (association with the state or outcome), and clinical utility (improved decision-making or outcomes). Regulatory approaches vary by jurisdiction and indication, with companion diagnostics sometimes required for targeted therapies. Limitations include variability across populations, preanalytical factors, cost, and the risk of false positives or negatives.