Biomarkers
Biomarkers are any measurable and quantifiable biological parameters which serve as indices for health- or disease-related processes. The idea of identifying biological markers as indicators for an underlying disease is an elementary concept in medicine.
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1 Introduction Biomarkers are any measurable and quantifiable biological parameters which serve as indices for health- or disease-related processes. The idea of identifying biological markers as indicators for an underlying disease is an elementary concept in medicine. Since the beginning of the medical skill of healing, signs and symptoms have been interpreted by medical doctors and guided diagnosis and treatment of their patients. With the emergence of the bioanalytical laboratory methods in the 50s of the last century a number of novel serum and urine markers became available. These objectively measurable serum markers were initially intended for studying physiological processes in biology. Over time, the value of such serum based biological markers for clinical decision making emerged as they were correlated with the pathology and the clinical course of disease states. This "traditional identification" of biomarkers as an observational site product of clinical practice led to the identification of the majority of clinical biomarkers employed in clinical practice today. Biomarker can be classified in two broad categories [1]. The first group are so-called "disease related biomarker". This class of biomarkers is intended to provide information about the individual risk of a patient to suffer from a disease in the future or the natural course of an already existing disease: •
Antecedent biomarkers are for identifying the risk of developing an illness in the future leading to preventive interventions for those at sufficient risk. Examples are the cancer susceptibility genes BRCAI and BRCA2 for breast cancer. This type of biomarker is currently intensively discussed from the background of personal genomic testing and the challenge to interpret the results in terms of clinical consequences.
Keywords: Biomarker, predictive, prognostic, screening, surrogate endpoint, clinical endpoint, cholesterol as biomarker
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Chapter 16: Biomarkers
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Screening biomarkers are intended for detecting subclinical disease enabling intervention at an earlier and potentially more curable stage than under usual clinical diagnostic conditions (e.g. PSA screening for prostate cancer). Diagnostic and staging biomarkers allowing clinicians to recognize overt disease and categorizing disease severity, respectively (e.g. Troponin T for acute coronary syndrome, pBNP for cardiomyopathy). Prognostic biomarkers for predicting future disease course and outcome of individual patients or groups of patients in terms of a clinical endpoint, including recurrence of disease (e.g. Her2 expression for breast cancer, cholesterol for CVD).
The second category of biomarker comprises the "therapy related biomarkers". It differs from the first group of biomarker in that it describes the response of the marker to a therapeutic intervention. This class of biomarkers includes:
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Predictive biomarkers are intended to predict the efficacy of a therapeutic inter vention before it is administered. Predictive biomarkers are context sensitive linking a sp
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