Serology is the scientific study of
serum and other
body fluid
Body fluids, bodily fluids, or biofluids, sometimes body liquids, are liquids within the human body. In lean healthy adult men, the total body water is about 60% (60–67%) of the total Human body weight, body weight; it is usually slightly lower ...
s. In practice, the term usually refers to the
diagnostic
Diagnosis is the identification of the nature and cause of a certain phenomenon. Diagnosis is used in many different disciplines, with variations in the use of logic, analytics, and experience, to determine " cause and effect". In systems engine ...
identification of
antibodies
An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the ...
in the serum.
Such antibodies are typically formed in response to an infection (against a given
microorganism
A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...
),
against other foreign proteins (in response, for example, to a
mismatched
''Mismatched'' is a 2020 Indian Hindi-language coming-of-age romantic drama web series on Netflix, based on Sandhya Menon's 2017 novel '' When Dimple Met Rishi''. It was adapted by Gazal Dhaliwal and directed by Akarsh Khurana and Nipun Dhar ...
blood transfusion
Blood transfusion is the process of transferring blood products into a person's circulation intravenously. Transfusions are used for various medical conditions to replace lost components of the blood. Early transfusions used whole blood, but mo ...
), or to one's own proteins (in instances of
autoimmune disease
An autoimmune disease is a condition arising from an abnormal immune response to a functioning body part. At least 80 types of autoimmune diseases have been identified, with some evidence suggesting that there may be more than 100 types. Nearly a ...
). In either case, the procedure is simple.
Serological tests
Serological tests are diagnostic methods that are used to identify antibodies and
antigens
In immunology, an antigen (Ag) is a molecule or molecular structure or any foreign particulate matter or a pollen grain that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response. ...
in a patient's sample. Serological tests may be performed to diagnose
infection
An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dise ...
s and
autoimmune illnesses, to check if a person has
immunity
Immunity may refer to:
Medicine
* Immunity (medical), resistance of an organism to infection or disease
* ''Immunity'' (journal), a scientific journal published by Cell Press
Biology
* Immune system
Engineering
* Radiofrequence immunity desc ...
to certain diseases, and in many other situations, such as determining an individual's
blood type
A blood type (also known as a blood group) is a classification of blood, based on the presence and absence of antibodies and inherited antigenic substances on the surface of red blood cells (RBCs). These antigens may be proteins, carbohydrate ...
.
Serological tests may also be used in
forensic serology Forensic serology is the detection, identification, classification, and study of various bodily fluids such as blood, semen, saliva, and urine, and their relationship to a crime scene. A forensic serologist may also be involved in DNA analysis and ...
to investigate crime scene evidence. Several methods can be used to detect antibodies and antigens, including
ELISA
The enzyme-linked immunosorbent assay (ELISA) (, ) is a commonly used analytical biochemistry assay, first described by Eva Engvall and Peter Perlmann in 1971. The assay uses a solid-phase type of enzyme immunoassay (EIA) to detect the presence ...
,
agglutination
In linguistics, agglutination is a morphological process in which words are formed by stringing together morphemes, each of which corresponds to a single syntactic feature. Languages that use agglutination widely are called agglutinative lang ...
,
precipitation
In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...
,
complement-fixation
The complement fixation test is an immunological medical test that can be used to detect the presence of either specific antibody or specific antigen in a patient's serum, based on whether complement fixation occurs. It was widely used to diagnos ...
, and
fluorescent antibodies and more recently
chemiluminescence
Chemiluminescence (also chemoluminescence) is the emission of light (luminescence) as the result of a chemical reaction. There may also be limited emission of heat. Given reactants A and B, with an excited intermediate ◊,
: + -> lozenge -> ...
.
Applications
Microbiology
![IgGIgM-Covid19-Test](https://upload.wikimedia.org/wikipedia/commons/0/02/IgGIgM-Covid19-Test.jpg)
In
microbiology
Microbiology () is the scientific study of microorganisms, those being unicellular (single cell), multicellular (cell colony), or acellular (lacking cells). Microbiology encompasses numerous sub-disciplines including virology, bacteriology, prot ...
, serologic tests are used to determine if a person has antibodies against a specific
pathogen
In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...
, or to detect antigens associated with a pathogen in a person's sample.
Serologic tests are especially useful for organisms that are difficult to
culture
Culture () is an umbrella term which encompasses the social behavior, institutions, and norms found in human societies, as well as the knowledge, beliefs, arts, laws, customs, capabilities, and habits of the individuals in these groups.Tyl ...
by routine laboratory methods, like ''
Treponema pallidum
''Treponema pallidum'', formerly known as ''Spirochaeta pallida'', is a spirochaete bacterium with various subspecies that cause the diseases syphilis, bejel (also known as endemic syphilis), and yaws. It is transmitted only among humans. It is ...
'' (the causative agent of
syphilis
Syphilis () is a sexually transmitted infection caused by the bacterium ''Treponema pallidum'' subspecies ''pallidum''. The signs and symptoms of syphilis vary depending in which of the four stages it presents (primary, secondary, latent, an ...
), or
virus
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea.
Since Dmitri Ivanovsky's 1 ...
es.
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
Immunoglobulin M (IgM) is one of several isotypes of antibody (also known as immunoglobulin) that are produced by vertebrates. IgM is the largest antibody, and it is the first antibody to appear in the response to initial exposure to an antig ...
(IgM) and
immunoglobulin G
Immunoglobulin G (Ig G) is a type of antibody. Representing approximately 75% of serum antibodies in humans, IgG is the most common type of antibody found in blood circulation. IgG molecules are created and released by plasma B cells. Each IgG a ...
(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.
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
Titer (American English) or titre (British English) is a way of expressing concentration. Titer testing employs serial dilution to obtain approximate quantitative information from an analytical procedure that inherently only evaluates as positiv ...
) is compared, and a significantly higher amount of IgG in the convalescent specimen suggests infection as opposed to previous exposure.
False negative results for antibody testing can occur in people who are
immunosuppressed
Immunosuppression is a reduction of the activation or efficacy of the immune system. Some portions of the immune system itself have immunosuppressive effects on other parts of the immune system, and immunosuppression may occur as an adverse reacti ...
, as they produce lower amounts of antibodies, and in people who receive
antimicrobial drugs early in the course of the infection.
Transfusion medicine
Blood typing
Blood compatibility testing is conducted in a medical laboratory to identify potential incompatibilities between blood group systems in blood transfusion. It is also used to diagnose and prevent some complications of pregnancy that can occur whe ...
is typically performed using serologic methods. The antigens on a person's red blood cells, which determine their
blood type
A blood type (also known as a blood group) is a classification of blood, based on the presence and absence of antibodies and inherited antigenic substances on the surface of red blood cells (RBCs). These antigens may be proteins, carbohydrate ...
, are identified using
reagent
In chemistry, a reagent ( ) or analytical reagent is a substance or compound added to a system to cause a chemical reaction, or test if one occurs. The terms ''reactant'' and ''reagent'' are often used interchangeably, but reactant specifies a ...
s that contain antibodies, called
antisera
Antiserum is a blood serum containing monoclonal or polyclonal antibodies that is used to spread passive immunity to many diseases via blood donation (plasmapheresis). For example, convalescent serum, passive antibody transfusion from a previous ...
. 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.
Other serologic methods used in
transfusion medicine
Transfusion medicine (or transfusiology) is the branch of medicine that encompasses all aspects of the transfusion of blood and blood components including aspects related to hemovigilance. It includes issues of blood donation, immunohematology ...
include
crossmatching and the direct and indirect
antiglobulin tests. Crossmatching is performed before a
blood transfusion
Blood transfusion is the process of transferring blood products into a person's circulation intravenously. Transfusions are used for various medical conditions to replace lost components of the blood. Early transfusions used whole blood, but mo ...
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.
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
Autoimmune hemolytic anemia (AIHA) occurs when antibodies directed against the person's own red blood cells (RBCs) cause them to burst (lyse), leading to an insufficient number of oxygen-carrying red blood cells in the circulation. The lifetime of ...
,
hemolytic disease of the newborn
Hemolytic disease of the newborn, also known as hemolytic disease of the fetus and newborn, HDN, HDFN, or erythroblastosis foetalis, is an alloimmune condition that develops in a fetus at or around birth, when the IgG molecules (one of the five ...
and
transfusion reaction
Blood transfusion is the process of transferring blood products into a person's Circulatory system, circulation intravenously. Transfusions are used for various medical conditions to replace lost components of the blood. Early transfusions used w ...
s.
The indirect antiglobulin test is used to screen for antibodies that could cause transfusion reactions and identify certain blood group antigens.
Immunology
Serologic tests can help to diagnose autoimmune disorders by identifying abnormal antibodies directed against a person's own tissues (
autoantibodies
An autoantibody is an antibody (a type of protein) produced by the immune system that is directed against one or more of the individual's own proteins. Many autoimmune diseases (notably lupus erythematosus) are associated with such antibodies.
Pr ...
).
All people have different immunology graphs.
Serological surveys
A 2016 research paper by Metcalf et al., amongst whom were
Neil Ferguson and
Jeremy Farrar
Sir Jeremy James Farrar (born 1 September 1961) is a British medical researcher who has served as director of the Wellcome Trust since 2013 and will serve as chief scientist at the World Health Organization in 2023. He was previously a professo ...
, stated that serological surveys are often used by
epidemiologist
Epidemiology is the study and analysis of the distribution (who, when, and where), patterns and risk factor, determinants of health and disease conditions in a defined population.
It is a cornerstone of public health, and shapes policy decision ...
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
Clinical study design is the formulation of trials and experiments, as well as observational studies in medical, clinical and other types of research (e.g., epidemiological) involving human beings. The goal of a clinical study is to assess the saf ...
, and
quantitative analysis, which could drive a
step change in our understanding and
optimum control of
infectious disease
An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dise ...
s."
In a helpful reply entitled "Opportunities and challenges of a World Serum Bank", de Lusignan and Correa observed
that the
In another helpful reply on the World Serum Bank, the Australian researcher
Karen Coates
Karen may refer to:
* Karen (name), a given name and surname
* Karen (slang), a term and meme for a demanding woman displaying certain behaviors
People
* Karen people, an ethnic group in Myanmar and Thailand
** Karen languages or Karenic l ...
declared that:
In April 2020,
Justin Trudeau
Justin Pierre James Trudeau ( , ; born December 25, 1971) is a Canadian politician who is the 23rd and current prime minister of Canada. He has served as the prime minister of Canada since 2015 and as the leader of the Liberal Party since 2 ...
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
The COVID-19 pandemic, also known as the coronavirus pandemic, is an ongoing global pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The novel virus was first identif ...
.
See also
*
Medical laboratory
A medical laboratory or clinical laboratory is a laboratory where tests are conducted out on clinical specimens to obtain information about the health of a patient to aid in diagnosis, treatment, and prevention of disease. Clinical Medical labor ...
*
Seroconversion
In immunology, seroconversion is the development of specific antibodies in the blood serum as a result of infection or immunization, including vaccination. During infection or immunization, antigens enter the blood, and the adaptive immune system ...
*
Serovar
A serotype or serovar is a distinct variation within a species of bacteria or virus or among immune cells of different individuals. These microorganisms, viruses, or cells are classified together based on their surface antigens, allowing the epi ...
*
Medical technologist
A medical laboratory scientist (MLS) or clinical laboratory scientist (CLS) or medical technologist (MT) performs diagnostic testing of blood and body fluids in clinical laboratories. The scope of a medical laboratory scientist's work begins wit ...
*
Dr. Geoffrey Tovey, noted serologist
*
Forensic serology Forensic serology is the detection, identification, classification, and study of various bodily fluids such as blood, semen, saliva, and urine, and their relationship to a crime scene. A forensic serologist may also be involved in DNA analysis and ...
References
External links
Serology(archived) –
MedlinePlus
MedlinePlus is an online information service produced by the United States National Library of Medicine. The service provides curated consumer health information in English and Spanish with select content in additional languages.
The site brings t ...
Medical Encyclopedia
*
{{Authority control
Clinical pathology
Blood tests
Epidemiology
Immunologic tests