Laboratoriummarkers

Laboratoriummarkers are measurable substances in biological samples that indicate biological states, processes, or responses to interventions. They are used to aid diagnosis, prognosis, treatment selection, and monitoring across medicine and research.

Markers can be endogenous, such as proteins, metabolites, nucleic acids, or cells produced by the body, or exogenous, such as administered drugs or environmental compounds. They are classified by application: diagnostic markers assist in identifying a disease; prognostic markers estimate likely outcomes; predictive markers forecast response to a therapy; and pharmacodynamic markers reflect a drug's effect.

Laboratory measurement employs a range of analytical methods, including immunoassays, enzymatic tests, chromatography, spectrometry, and nucleic acid amplification. Assay design and calibration aim to ensure accuracy, precision, sensitivity, and specificity. Pre-analytical factors like specimen type, collection time, handling, and patient characteristics can influence results, as can biological variation between individuals and within individuals over time. Reference ranges and decision thresholds are typically lab- and method-specific.

Examples of well-known laboratory markers include troponin for myocardial injury; HbA1c for long-term glucose control; lipid panel components such as LDL cholesterol; C-reactive protein as a non-specific inflammation marker; creatinine and estimated glomerular filtration rate for kidney function; D-dimer for thrombotic activity; B-type natriuretic peptide for heart failure; and prostate-specific antigen for prostate cancer screening.

Limitations of laboratory markers include potential false positives or negatives, biological variability, and interference from medications or other substances. Markers are most informative when interpreted in the clinical context alongside patient history, imaging, and other tests. Standardization efforts aim to harmonize assays and establish universally applicable reference ranges.