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{{short description|Scientific study of serum and other bodily fluids}}
'''Serology''' is the scientific study of [[Serum (blood)|serum]] and other [[body fluid]]s. In practice, the term usually refers to the [[medical diagnosis|diagnostic]] identification of [[Antibody|antibodies]] in the serum.<ref name=Sherris>{{cite book | veditors = Ryan KJ, Ray CG | title = Sherris Medical Microbiology | url = https://archive.org/details/sherrismedicalmi00ryan | url-access = limited | edition = 4th | pages = [https://archive.org/details/sherrismedicalmi00ryan/page/n264 247]–9 |publisher = McGraw Hill | year = 2004 | isbn = 978-0-8385-8529-0 }}</ref> Such antibodies are typically formed in response to an infection (against a given [[microorganism]]),<ref name=Baron>{{cite book | author = Washington JA | chapter = Principles of Diagnosis: Serodiagnosis |title=Baron's Medical Microbiology |veditors=Baron S, et al.| edition = 4th | publisher = Univ of Texas Medical Branch | year = 1996 | chapter-url = https://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=mmed.section.5462 | isbn = 978-0-9631172-1-2}}</ref> against other foreign proteins (in response, for example, to a [[Acute hemolytic transfusion reaction|mismatched]] [[blood transfusion]]), or to one's own proteins (in instances of [[autoimmune disease]]). In either case, the procedure is simple.{{cn|date=April 2022}}
==Serological tests==
Serological tests are diagnostic methods that are used to identify antibodies and [[antigens]] in a patient's sample. Serological tests may be performed to diagnose [[infection]]s and [[autoimmune illness]]es, to check if a person has [[immunity (medical)|immunity]] to certain diseases, and in many other situations, such as determining an individual's [[blood type]].<ref name=Sherris /> Serological tests may also be used in [[forensic serology]] to investigate crime scene evidence.<ref>{{cite book |last1=Gardner |first1=Ross M. |title=Practical crime scene processing and investigation |date=2011 |publisher=CRC Press |edition=Second}}</ref> Several methods can be used to detect antibodies and antigens, including [[ELISA]],<ref>{{cite web|title=Enzyme-linked immunosorbent assay (ELISA)
|publisher=British Society for Immunology|url=https://www.immunology.org/public-information/bitesized-immunology/experimental-techniques/enzyme-linked-immunosorbent-assay}}</ref> [[Agglutination (biology)|agglutination]], [[Precipitation (chemistry)|precipitation]], [[complement-fixation]], and [[direct fluorescent antibody|fluorescent antibodies]] and more recently [[chemiluminescence]].<ref>{{Citation|last=Atmar|first=Robert L.|title=Immunological Detection and Characterization|date=2014|url=http://dx.doi.org/10.1007/978-1-4899-7448-8_3|work=Viral Infections of Humans|pages=47–62|place=Boston, MA|publisher=Springer US|doi=10.1007/978-1-4899-7448-8_3|isbn=978-1-4899-7447-1|s2cid=68212270|access-date=2021-06-13}}</ref>
===Applications===
====Microbiology====
[[File:IgGIgM-Covid19-Test.jpg|thumb|upright=0.5|IgG and IgM [[rapid diagnostic test]] for [[COVID-19]]]]
In [[microbiology]], '''serologic tests''' are used to determine if a person has antibodies against a specific [[pathogen]], or to detect antigens associated with a pathogen in a person's sample.<ref name="Turgeon2015"/>  Serologic tests are especially useful for organisms that are difficult to [[Culture (microbiology)|culture]] by routine laboratory methods, like ''[[Treponema pallidum]]'' (the causative agent of [[syphilis]]), or [[virus]]es.<ref name="BerkowitzJerris2016"/>
The presence of antibodies against a pathogen in a person's blood indicates that they have been exposed to that pathogen. Most serologic tests measure one of two types of antibodies: [[immunoglobulin M]] (IgM) and [[immunoglobulin G]] (IgG). IgM is produced in high quantities shortly after a person is exposed to the pathogen, and production declines quickly thereafter. IgG is also produced on the first exposure, but not as quickly as IgM. On subsequent exposures, the antibodies produced are primarily IgG, and they remain in circulation for a prolonged period of time.<ref name="Turgeon2015"/>
This affects the interpretation of serology results: a positive result for IgM suggests that a person is currently or recently infected, while a positive result for IgG and negative result for IgM suggests that the person may have been infected or immunized in the past. Antibody testing for infectious diseases is often done in two phases: during the initial illness (acute phase) and after recovery (convalescent phase). The amount of antibody in each specimen ([[antibody titer]]) is compared, and a significantly higher amount of IgG in the convalescent specimen suggests infection as opposed to previous exposure.<ref name="MahonLehman2018">{{cite book|author1=Connie R. Mahon|author2=Donald C. Lehman|author3=George Manuselis|title=Textbook of Diagnostic Microbiology - E-Book|url=https://books.google.com/books?id=uGRgDwAAQBAJ|date=18 January 2018|publisher=Elsevier Health Sciences|isbn=978-0-323-48212-7|pages=193–4}}</ref> False negative results for antibody testing can occur in people who are [[immunosuppressed]], as they produce lower amounts of antibodies, and in people who receive [[antimicrobial drug]]s early in the course of the infection.<ref name="BerkowitzJerris2016">{{cite book|author1=Frank E. Berkowitz|author2=Robert C. Jerris|title=Practical Medical Microbiology for Clinicians|url=https://books.google.com/books?id=RktICgAAQBAJ|date=15 February 2016|publisher=John Wiley & Sons|isbn=978-1-119-06674-3|pages=24–25}}</ref>
====Transfusion medicine====
[[File:Blood typing by manual tube method - type O positive.jpg|thumb|upright=0.75|O positive blood type: the patient's red cells are agglutinated by Anti-D (anti-Rh factor) antisera, but not by anti-A and anti-B antisera. The patient's plasma agglutinates type A and B red cells.]]
[[Blood typing]] is typically performed using serologic methods. The antigens on a person's red blood cells, which determine their [[blood type]], are identified using [[reagent]]s that contain antibodies, called [[antisera]]. When the antibodies bind to red blood cells that express the corresponding antigen, they cause red blood cells to clump together (agglutinate), which can be identified visually. The person's blood group antibodies can also be identified by adding plasma to cells that express the corresponding antigen and observing the agglutination reactions.<ref name="Harmening2018">{{cite book|author=Denise M Harmening|title=Modern Blood Banking & Transfusion Practices|url=https://books.google.com/books?id=vxyDDwAAQBAJ|date=30 November 2018|publisher=F.A. Davis|isbn=978-0-8036-9462-0|pages=65, 261}}</ref><ref name="Turgeon2015">{{cite book|author=Mary Louise Turgeon|title=Linne & Ringsrud's Clinical Laboratory Science - E-Book: The Basics and Routine Techniques|url=https://books.google.com/books?id=D1umBgAAQBAJ|date=10 February 2015|publisher=Elsevier Health Sciences|isbn=978-0-323-37061-5|pages=586–95,543,556}}</ref>
Other serologic methods used in [[transfusion medicine]] include [[crossmatching]] and the direct and indirect [[antiglobulin test]]s. Crossmatching is performed before a [[blood transfusion]] to ensure that the donor blood is compatible. It involves adding the recipient's plasma to the donor blood cells and observing for agglutination reactions.<ref name="Harmening2018"/> The direct antiglobulin test is performed to detect if antibodies are bound to red blood cells inside the person's body, which is abnormal and can occur in conditions like [[autoimmune hemolytic anemia]], [[hemolytic disease of the newborn]] and [[transfusion reaction]]s.<ref name="LTO-D">{{cite web|author=American Association for Clinical Chemistry|title=Direct Antiglobulin Test|date=24 December 2019|access-date=24 April 2020|url=https://labtestsonline.org/tests/direct-antiglobulin-test|work=Lab Tests Online|author-link=American Association for Clinical Chemistry}}</ref>  The indirect antiglobulin test is used to screen for antibodies that could cause transfusion reactions and identify certain blood group antigens.<ref name="McPherson2011">{{cite book|author1=Richard A. McPherson|author2=Matthew R. Pincus|title=Henry's Clinical Diagnosis and Management by Laboratory Methods|url=https://books.google.com/books?id=-97J-8Zh2hkC&pg=PA714|date=6 September 2011|publisher=Elsevier Health Sciences|isbn=978-1-4557-2684-4|pages=714–5}}</ref>
[[File:Serology interpretation of antibody panel for blood group antigens.jpg|thumb|center|350px|Interpretation of antibody panel used in serology to detect patient antibodies towards the most relevant [[human blood group systems]]. {{further|Blood compatibility testing}}]]
====Immunology====
Serologic tests can help to diagnose autoimmune disorders by identifying abnormal antibodies directed against a person's own tissues ([[autoantibodies]]).<ref name="LTO-A">{{cite web|author=American Association for Clinical Chemistry|title=Autoantibodies|date=13 November 2019|access-date=24 April 2020|url=https://labtestsonline.org/tests/autoantibodies|work=Lab Tests Online|author-link=American Association for Clinical Chemistry}}</ref> All people have different immunology graphs.{{cn|date=December 2022}}
== Serological surveys ==
A 2016 research paper by Metcalf et al., amongst whom were [[Neil Ferguson (epidemiologist)|Neil Ferguson]] and [[Jeremy Farrar]], stated that serological surveys are often used by [[epidemiologist]]s to determine the prevalence of a disease in a population. Such surveys are sometimes performed by random, anonymous sampling from samples taken for other medical tests or to assess the prevalence of antibodies of a specific organism or protective titre of antibodies in a population. Serological surveys are usually used to quantify the proportion of people or animals in a population positive for a specific antibody or the titre or concentrations of an antibody. These surveys are potentially the most direct and informative technique available to infer the dynamics of a population's susceptibility and level of immunity. The authors proposed a [[World Serology Bank]] (or serum bank) and foresaw "associated major methodological developments in serological testing, [[study design]], and [[quantitative analysis (chemistry)|quantitative analysis]], which could drive a [[step change]] in our understanding and [[optimum control]] of [[infectious disease]]s."<ref name="metcalf">{{cite journal |doi=10.1016/S0140-6736(16)30164-7|title=Use of serological surveys to generate key insights into the changing global landscape of infectious disease|year=2016|last1=Metcalf|first1=C Jessica E.|last2=Farrar|first2=Jeremy|author-link2=Jeremy Farrar|last3=Cutts|first3=Felicity T.|last4=Basta|first4=Nicole E.|last5=Graham|first5=Andrea L.|author-link5=Andrea L. Graham|last6=Lessler|first6=Justin|last7=Ferguson|first7=Neil M.|author-link7=Neil Ferguson (epidemiologist)|last8=Burke|first8=Donald S.|author-link8=Donald Burke|last9=Grenfell|first9=Bryan T.|author-link9=Bryan Grenfell|journal=The Lancet|volume=388|issue=10045|pages=728–730|pmid=27059886|pmc=5678936}}</ref>
In a helpful reply entitled "Opportunities and challenges of a World Serum Bank", de Lusignan and Correa observed<ref name="dlc">{{cite journal |doi=10.1016/S0140-6736(17)30046-6|title=Opportunities and challenges of a World Serum Bank|year=2017|last1=De Lusignan|first1=Simon|last2=Correa|first2=Ana|journal=The Lancet|volume=389|issue=10066|pages=250–251|pmid=28118910|s2cid=42914918 |doi-access=}}</ref> that the {{cquote|principal [[ethical]] and logistical challenges that need to be overcome are the methods of obtaining specimens, how [[informed consent]] is acquired in busy practices, and the filling in of gaps in [[patient sampling]].}}
In another helpful reply on the World Serum Bank, the Australian researcher [[Karen Coates]] declared that:<ref name="coates">{{cite journal |doi=10.1016/S0140-6736(17)30052-1|title=Opportunities and challenges of a World Serum Bank|year=2017|last1=Coates|first1=Karen M.|journal=The Lancet|volume=389|issue=10066|pages=251–252|pmid=28118912|doi-access=free}}</ref>
{{cquote|Improved serological surveillance would allow [[governments]], [[aid agencies]], and [[policy writer]]s to direct [[public health]] resources to where they are needed most. A better understanding of [[infection dynamics]] with respect to the [[Global warming|changing patterns of global weather]] should inform policy measures including where to concentrate [[vaccination]] efforts and [[insect control]] measures.}}
In April 2020, [[Justin Trudeau]] formed the [[COVID-19 Immunity Task Force]], whose mandate is to carry out a serological survey in a scheme hatched in the midst of the [[COVID-19 pandemic]].<ref name="cbcvk">{{cite news |title=WHO set pandemic response back by 2-3 weeks, says doctor on new federal task force |url=https://www.cbc.ca/news/politics/naylor-china-who-data-trust-1.5543281 |publisher=CBC |date=23 April 2020}}</ref><ref name="pmgc">{{cite web |title=Prime Minister announces new support for COVID-19 medical research and vaccine development |url=https://pm.gc.ca/en/news/news-releases/2020/04/23/prime-minister-announces-new-support-covid-19-medical-research-and |publisher=Justin Trudeau, Prime Minister of Canada |date=23 April 2020}}</ref>
== See also ==
* [[Forensic serology]]
* [[Medical laboratory]]
* [[Medical technologist]]
* [[Seroconversion]]
* [[Serovar]]
* [[Geoffrey Tovey]], noted serologist
==References==
{{Reflist|2}}
==External links==
{{Commons category}}
* [https://web.archive.org/web/20120217140428/http://www.nlm.nih.gov/medlineplus/ency/article/003511.htm Serology] <small>(archived)</small> – [[MedlinePlus]] Medical Encyclopedia
* {{MeshName|Serologic+Tests}}
{{pathology}}
{{Immunologic techniques and tests}}
{{Blood tests}}
{{Authority control}}
[[Category:Serology| ]]
[[Category:Clinical pathology]]
[[Category:Blood tests]]
[[Category:Epidemiology]]
[[Category:Immunologic tests]]