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A biomarker, or biological marker, is in general a substance used as an indicator of a biological state. It is a characteristic that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention. It is used in many scientific fields.

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Biomarkers in Medicine

Biomarkers are characteristic biological properties that can be detected and measured in parts of the body like the blood or tissue. They may indicate either normal or diseased processes in the body.[1] Biomarkers can be specific cells, molecules, or genes, gene products, enzymes, or hormones. Complex organ functions or general characteristic changes in biological structures can also serve as biomarkers. Although the term biomarker is relatively new, biomarkers have been used in pre-clinical research and clinical diagnosis for a considerable time.[2]

For example, body temperature is a well-known biomarker for fever. Blood pressure is used to determine the risk of stroke. It is also widely known that cholesterol values are a biomarker and risk indicator for coronary and vascular disease, and that C-reactive protein (CRP) is a marker for inflammation.

Disease-related Biomarkers and Drug-related Biomarkers

It is necessary to distinguish between disease-related and drug-related biomarkers. Disease-related biomarkers give an indication of whether there is a threat of disease (risk indicator or predictive biomarkers), if a disease already exists (diagnostic biomarker), or how such a disease may develop in an individual case (prognostic biomarker). In contrast, drug-related biomarkers indicate whether a drug will be effective in a specific patient and how the patient’s body will process it.

In addition to long-known parameters, such as those included and objectively measured in a blood count, there are numerous novel biomarkers used in the various medical specialties. Currently, intensive work is taking place on the discovery and development of innovative and more effective biomarkers. These "new" biomarkers have become the basis for preventive medicine, meaning medicine that recognises diseases or the risk of disease early, and takes specific countermeasures to prevent the development of disease. Biomarkers are also seen as the key to personalised medicine, treatments individually tailored to specific patients for highly efficient intervention in disease processes. Often, such biomarkers indicate changes in metabolic processes.

The "classic" biomarker in medicine is a laboratory parameter that the doctor can use to help make decisions in making a diagnosis and selecting a course of treatment. For example, the detection of certain autoantibodies in patient blood is a reliable biomarker for autoimmune disease, and the detection of rheumatoid factors has been an important diagnostic marker for rheumatoid arthritis (RA) for over 50 years.[3] [4] For the diagnosis of this autoimmune disease the antibodies against the bodies own citrullinated proteins are of particular value. These ACPAs, (ACPA stands for Anti-citrullinated protein/peptide antibody) can be detected in the blood before the first symptoms of RA appear. They are thus valuable and highly predictive biomarkers for the early diagnosis of this autoimmune disease.[5] In addition, they indicate if the disease threatens to be severe with serious damage to the bones and joints[6] [7], which is an important tool for the doctor when providing a diagnosis and developing a treatment plan.

There are also more and more indications that ACPAs can be very useful in monitoring the success of treatment for RA.[8] This would make possible the accurate use of modern treatments with biologicals. Physicians hope to soon be able to individually tailor rheumatoid arthritis treatments for each patient.

According to Häupl T. et al. prediction of response to treament will become the most important aim of biomarker research in medicine. With the growing number of new biological agents, there is increasing pressure to identify molecular parameters such as ACPAs that will not only guide the therapeutic decision but also help to define the most important targets for which new biological agents should be tested in clinical studies.[9]

Biomarkers in Drug Development

Once a proposed biomarker has been validated, it can be used to diagnose disease risk, presence of disease in an individual, or to tailor treatments for the disease in an individual (choices of drug treatment or administration regimes). In evaluating potential drug therapies, a biomarker may be used as a surrogate for a natural endpoint such as survival or irreversible morbidity. If a treatment alters the biomarker, which has a direct connection to improved health, the biomarker serves as a surrogate endpoint for evaluating clinical benefit.

Biomarker requirements

For chronic diseases, whose treatment may require patients to take medications for years, accurate diagnosis is particularly important, especially when strong side effects are expected from the treatment. In these cases, biomarkers are becoming more and more important, because they can confirm a difficult diagnosis or even make it possible in the first place.[10] A number of diseases, such as Alzheimer’s disease or rheumatoid arthritis, often begin with an early, symptom-free phase. In such symptom-free patients there may be more or less probability of actually developing symptoms. In these cases, biomarkers help to identify high-risk individuals reliably and in a timely manner so that they can either be treated before onset of the disease or as soon as possible thereafter.[11] [12]

In order to use a biomarker for diagnostics, the sample material must be as easy to obtain as possible. This may be a blood sample taken by a doctor, a urine or saliva sample, or a drop of blood like those diabetes patients extract from their own fingertips for regular blood-sugar monitoring.

For rapid initiation of treatment, the speed with which a result is obtained from the biomarker test is critical. A rapid test, which delivers a result after only a few minutes, is optimal. This makes it possible for the physician to discuss with the patient how to proceed and if necessary to start treatment immediately after the test.

Naturally, the detection method for a biomarker must be accurate and as easy to carry out as possible. The results from different laboratories may not differ significantly from each other, and the biomarker must naturally have proven its effectiveness for the diagnosis, prognosis, and risk assessment of the affected diseases in independent studies.

Biomarkers in Medicine: Types

Biomarkers validated by genetic and molecular biology methods can be classified into three types.

  • Type 0 - Natural history markers
  • Type 1 - Drug activity markers
  • Type 2 - Surrogate markers

Geology, astrobiology, and biochemistry

A biomarker can be any kind of molecule indicating the existence, past or present, of living organisms. In the fields of geology and astrobiology, biomarkers are also known as biosignatures. The term biomarker is also used to describe biological involvement in the generation of petroleum.

Medicine

In medicine, a biomarker can be a substance that is introduced into an organism as a means to examine organ function or other aspects of health. For example, rubidium chloride is used as a radioactive isotope to evaluate perfusion of heart muscle. It can also be a substance whose detection indicates a particular disease state, for example, the presence of an antibody may indicate an infection. More specifically, a biomarker indicates a change in expression or state of a protein that correlates with the risk or progression of a disease, or with the susceptibility of the disease to a given treatment.

Psychiatry

In psychiatric research, a fruitful way of finding genetic causes for diseases such as schizophrenia has been the use of a special kind of biomarker called an endophenotype.

Cell biology

In cell biology, a biomarker is a molecule that allows for the detection and isolation of a particular cell type (for example, the protein Oct-4 is used as a biomarker to identify embryonic stem cells). See a recent publicaiton for more material on biomarkers in Psychiatry. Biomarkers for Psychiatric Disorders Publisher Springer US DOI 10.1007/978-0-387-79251-4 Copyright 2009 ISBN 978-0-387-79250-7 (Print) 978-0-387-79251-4 (Online) Subject Collection Biomedical and Life Sciences Subject Biomedicine, Psychiatry, Proteomics, Molecular Medicine and Neurosciences SpringerLink Date Wednesday, April 29, 2009

Exposure assessment

A biomarker can also be used to indicate exposure to various environmental substances in epidemiology and toxicology. In these cases, the biomarker may be the external substance itself (e.g. asbestos particles or NNK from tobacco), or a variant of the external substance processed by the body (a metabolite). (See also: Bioindicator.)

Genetics

In genetics, a biomarker (identified as genetic marker) is a fragment of DNA sequence that causes disease or is associated with susceptibility to disease.

See also

Genomic marker are polymorphic genes or mutent genes or genes with loss of heterozygus condition, which useful for identification of disease or identification present stage of disease before or after therapy.

References

  1. ^ http://www.biomarkersconsortium.org
  2. ^ http://www.biomarker.co.uk/whatisabiomarkers.html
  3. ^ Waaler E. "On the occurrence of a factor in human serum activating the specific agglutintion of sheep blood corpuscles. 1939". APMIS 2007 (May) 115 (5): 422–38.  
  4. ^ Rose HM, Ragan E, Pearce E, Lipman MO. "Differential agglutination of normal and sensitized sheep erythrocytes by sera of patients with rheumatoid arthritis". Proc Soc Exp Biol Med. 1948 May;68(1):1-6..  
  5. ^ Bang H, Egerer K, Gauliard A, Lüthke K, Rudolph PE, Fredenhagen G et al.. "Mutation and citrullination modifies vimentin to a novel autoantigen for rheumatoid arthritis". Arthritis Rheum 2007; 56(8):2503-11.  
  6. ^ Szodoray P, Szabó Z, Kapitány A, Gyetvai A, Lakos G, Szántó S, Szücs G, Szekanecz Z. "Anti-citrullinated protein/peptide autoantibodies in association with genetic and environmental factors as indicators of disease outcome in rheumatoid arthritis.". Autoimmun Rev. 2009 May 6. [Epub ahead of print].  
  7. ^ Mathsson L, Mullazehi M, Wick MC, Sjöberg O, van Vollenhoven R, Klareskog L, Rönnelid J. "Antibodies against citrullinated vimentin in rheumatoid arthritis: higher sensitivity and extended prognostic value concerning future radiographic progression as compared with antibodies against cyclic citrullinated peptides.". Arthritis Rheum. 2008 Jan;58(1):36-45..  
  8. ^ Nicaise Roland P, Grootenboer Mignot S, Bruns A, Hurtado M, Palazzo E, Hayem G, Dieudé P, Meyer O, Chollet Martin S. "Antibodies to mutated citrullinated vimentin for diagnosing rheumatoid arthritis in anti-CCP-negative patients and for monitoring infliximab therapy". Arthritis Res Ther. 2008;10(6):R142..  
  9. ^ Häupl T, Stuhlmüller B, Grützkau A, Radbruch A, Burmester GR. "Does gene expression analysis inform us in rheumatoid arthritis?". Ann Rheum Dis. 2010 Jan;69 Suppl 1:i37-42. http://www.ncbi.nlm.nih.gov/pubmed/19995742?dopt=Abstract.  
  10. ^ Pharma Matters White Paper: Establishing the standards in biomarker research (2008). Thomson Reuters
  11. ^ Craig-Schapiro R, Fagan AM, Holtzman DM. "Biomarkers of Alzheimer's disease". Neurobiol Dis. 2008 Oct 28..  
  12. ^ Egerer K, Feist E, Burmester G. "The Serological Diagnosis of Rheumatoid Arthritis – Antibodies to citrullinated Antigens". Dtsch Arztebl Int 2009; 106(10): 159-63.  







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