Serology is a branch of immunology that studies the response of antigens to serum antibodies.
Serological studies are a technique for studying certain antibodies or antigens in the blood serum of patients. They are based on immune responses. These studies are widely used in the process of diagnosing various infectious diseases and in determining the blood type of a person.
Who is assigned a serological examination
Serological analysis is prescribed to patients with suspected infectious disease. This analysis in conflicting situations with the diagnosis will help establish the causative agent of the disease. Further treatment also largely depends on the results of serological studies, since the determination of a specific microorganism contributes to the appointment of a specific treatment.
What material is being studied
Serological studies involve the collection of biological material from the patient in the form of:
- blood serum;
- saliva;
- fecal masses.
The material should be in the laboratory as soon as possible. Otherwise, it can be stored in the refrigerator at a temperature of +4 or by adding a preservative.
Testing
It is not necessary to specially prepare the patient for the collection of these analyzes. Research is safe. A blood test is taken in the morning on an empty stomach, both from the ulnar vein and from the ring finger. After sampling, the blood should be placed in a sterile, sealed tube.
Blood serology
Human blood performs many functions in the body and has a very wide field of activity, therefore, there are many options for blood tests. One of them is serological blood tests. This is a basic analysis carried out with the aim of recognizing certain microbes, viruses and infections, as well as the stage of development of the infectious process. Serological blood tests are used for:
- determination of the number of antibodies against viruses and microbes in the body. For this, the antigen of the pathogen is added to the blood serum, after which the ongoing chemical reaction is evaluated;
- determination of antigen by introducing antibodies into the blood ;
- blood type definitions.
Serological blood tests are always prescribed twice - to determine the dynamics of the development of the disease. A single determination of the interaction of antigens and antibodies indicates only the fact of infection. To reflect the full picture, where you can observe an increase in the number of bonds between immunoglobulins and antigens, a second study is necessary.
Serological studies: analyzes and their interpretation
An increase in the number of antigen-antibody complexes in the body indicates the presence of infection in the patient's body. Conducting specific chemical reactions with the growth of these indicators in the blood contribute to the determination of the disease and its stage.
If the result of the analysis shows the absence of antibodies to pathogens, then this indicates the absence of infection of the body. However, this rarely happens, since the appointment of a serological analysis already indicates the detection of symptoms of a particular infection.
What may affect the result of the analysis
Care should be taken to monitor the conditions under which blood is taken. It is impossible to prevent the entry into the blood of something extraneous. The day before the analysis, you should not overload the body with fatty foods, alcohol and sugary drinks. Stressful situations should be excluded and physical activity reduced. Biological material should be delivered to the laboratory as soon as possible, as long-term storage of serum leads to partial inactivity of antibodies.
Serological research methods
In laboratory practice, serological blood tests are complementary to bacteriological studies. The main methods are presented:
1. The fluorescence reaction, which is carried out in two stages. First, antibodies are detected in the circulating antigen complex. Then an antiserum is applied to the control sample, followed by incubation of the preparations. RIF is used to quickly detect the causative agent of the disease in the test material. Reaction results are evaluated using a luminescent microscope. The nature of the glow, shape, size of objects is estimated.
2. The agglutination reaction, which is a simple reaction of gluing discrete antigens with antibodies. Allocate:
- direct reactions used to detect antibodies in the patient's blood serum. A certain amount of dead microbes is added to the serum and causes the formation of sediment in the form of flakes. Serological tests for typhoid imply a direct agglutination reaction;
- reactions of passive hemagglutonation, based on the ability of red blood cells to adsorb antigen on its surface and cause adhesion upon contact with the antibody, and the appearance of a visible precipitate. It is used in the process of diagnosing infectious diseases to identify hypersensitivity to certain drugs. When evaluating the results, the appearance of the sediment is taken into account. A ring-shaped pellet at the bottom of the tube indicates a negative reaction. Lacy sediment with uneven edges indicates the presence of a particular infection.
3. Enzyme-linked immunosorbent assay, which is based on the principle of attachment of the enzyme label to antibodies. This allows you to see the result of the reaction by the appearance of enzyme activity or by a change in its level. This research method has several advantages:
- very sensitive;
- the reagents used are universal, and they are stable for six months;
- the process of recording the results of the analysis is automated.
The above listed serological research methods have some advantages over the bacteriological method. These methods allow you to determine the antigens of pathogens in a few minutes or hours. Moreover, these studies can detect pathogen antigens even after treatment and the death of the bacteria that cause it.
Diagnostic value of the study
The results of serological studies are a valuable diagnostic method, but have auxiliary significance. The basis for the diagnosis is still clinical data. Serological studies are done to confirm the diagnosis if the reactions do not contradict the clinical picture. Weakly positive reactions of serological studies without a clinical picture confirming it cannot become the basis for a diagnosis. Such results should be taken into account when a patient has had a similar disease in the past and has undergone appropriate treatment.
Determination of hereditary signs of blood, confirmation or refutation of paternity, the study of hereditary and autoimmune diseases, the establishment of the nature and source of infection in epidemics - all this helps to identify serological blood tests. Deciphering the results gives information about the presence of specific proteins for infections such as syphilis, hepatitis, HIV, toxoplasmosis, rubella, measles, typhoid fever.