Serological tests play a key role in the diagnosis of many diseases, helping doctors assess the patient's immune status and detect the presence of various pathogens, such as viruses, bacteria, and parasites. Serology is a branch immunology, which studies the reactions occurring between antigens a antibodies in blood serum. Thanks to this method, we can precisely determine whether the patient's body has had contact with a given pathogen and what immune response it has produced.
What do serological tests involve?
Serological tests consist in identifying and assessing the presence of antigens and antibodies in a sample taken from a patient, most often in blood serum. Antigens are molecules recognized by the immune system as foreign, e.g. bacteria, viruses, parasites (MICROBIOLOGY), and even allergens. The immune system responds to antigens by producing specific antibodies to fight the threat.
An example of a reaction between an antigen and an antibody is the formation of so-called immune complexes, which are key in the diagnostic process. Serological tests measure the concentration of these complexes, which allows for the detection of infectious diseases, allergies, and some autoimmune diseases.
Types of serological tests
There are many research methods in serology that differ in the way they detect and label antigens or antibodies. The most popular serological methods include:
- Agglutination test – a method used, among others, to determine blood groups and detect antibodies against known antigens. This test also enables the diagnosis of some bacterial diseases.
- Neutralization Test – allows for the detection and quantification of antibodies that neutralize the virus. It is used, for example, in the diagnosis of viral diseases such as influenza.
- Complement fixation test – a method used in the diagnosis of bacterial, viral and fungal diseases such as syphilis, influenza and listeriosis.
- ELISA immunoenzymatic test – precise and fast method allowing quantitative or semi-quantitative detection of antigens and antibodies. It is widely used, among others, in the diagnosis of Lyme disease and viral infections.
- Immunofluorescence test – a method for detecting viral and bacterial antigens, e.g. RSV or Chlamydia trachomatis, thanks to the use of antibodies labeled with fluorescent dyes.
Antibody classes
The antibodies we detect in serological tests are divided into different classes that perform different functions in the immune response:
- IgM – IgM antibodies are produced by the body at an early stage of infection. They are the first line of defense in the fight against a newly emerging pathogen. A high level of IgM in the patient's blood may indicate an active, fresh infection.
- IgG – IgG antibodies are produced later, but are more durable and can remain in the body for a long time. Their presence indicates a past infection or acquired immunity to a given pathogen. IgG is particularly important in assessing immunity to diseases such as measles, chickenpox or COVID-19.
- IgE – Antibodies associated with allergic reactions. Their elevated levels may indicate an allergy to a specific allergen.
When are serological tests performed?
Serological tests are used in a wide range of diagnostics, both for detecting infectious diseases and assessing the patient's immune status. Below are some situations in which serological tests are necessary:
- Diagnostics of infectious diseases – Detection of pathogens such as viruses (influenza, human papillomavirus, HIV), bacteria (syphilis, Lyme disease), or parasites (e.g. Giardia lamblia).
- Assessment of immune status – Serological tests are used to check whether a patient has developed appropriate antibodies after contact with a pathogen, which may indicate immunity to the disease.
- Blood transfusions and transplants – Serology plays a key role in research related to determining blood type and tissue compatibility in transplantation.
- Allergy diagnostics – Serological tests allow for the determination of the level of IgE antibodies, which is crucial in the assessment of allergic reactions.
- Serological conflict – Serological tests are essential for diagnosis serological conflict, which can occur when the mother and fetus have incompatible blood groups. This can lead to serious complications such as hemolytic disease of the newborn.
Serological conflict
Serological conflict is a situation in which there is an incompatibility between the blood groups of the mother and the fetus, which can cause an immune reaction in the mother's body against the baby's blood cells. This phenomenon is especially dangerous when the mother has a blood group Rh- and the fetus Rh+. In such a situation, the mother's immune system begins to produce antibodies, which can attack the fetus's red blood cells. An undiagnosed serological conflict can lead to hemolytic disease newborn.
To prevent complications, pregnant women are serologically tested for the presence of antibodies against the Rh antigen. Thanks to the early detection of serological conflict, appropriate treatment can be implemented, which minimizes the risk to the fetus.
What does a serological test look like?
In order to perform a serological test, blood is usually taken from the patient. Depending on the purpose of the test, other biological materials such as urine, saliva or stool can also be used. The testing process is based on the assessment of the antigen-antibody reaction in the sample taken from the patient. The results of serological tests can be both qualitative (whether antigens or antibodies are present) and quantitative, determining the level of antibodies.
The waiting time for the result depends on the method used in the laboratory. Modern techniques such as ELISA tests – using tiles for Elisa, or chemiluminescent immunological tests (CLIA), allow for a quick and precise assessment of the patient's immune status.
Summary
Serological tests is an extremely important diagnostic tool in medicine. They can be used not only to detect infectious diseases, assess the body's resistance to specific pathogens, but also diagnose allergies and some autoimmune diseases. Serological methods, such as ELISA tests or agglutination tests, enable precise analysis of the reaction between antigen and antibody, which is crucial in the diagnosis of many diseases.
If you want to know more about Serological tests, visit our website where you will find a full range of tests and information on how to prepare for the test. Serology is a branch of medicine that is still developing dynamically, bringing new diagnostic possibilities in many areas of health.
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