Serology is a branch of immunology that studies the reactions of antigens to serum antibodies.
Serological testing is 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 human blood group.
Who is assigned a serological test
Serological testing is given to patients with suspected infectious disease. This analysis in conflicting situations with the diagnosis will help to establish the causative agent of the disease. Also, further treatment largely depends on the results of serological studies, since the identification of a specific microorganism contributes to the appointment of a specific treatment.
What material is being tested
Serological studies involve taking biological material from a patient in the form:
- blood serum;
- saliva;
- fecalwt.
The material should be in the laboratory as soon as possible. Otherwise, it can be stored in the refrigerator at +4 or by adding a preservative.
Sampling
There is no need to specially prepare the patient for the collection of test data. Research is safe. A blood test is taken in the morning on an empty stomach, both from the cubital vein and from the ring finger. After sampling, blood should be placed in a sterile, sealed tube.
Serological blood test
Human blood performs many functions in the body and has a very wide field of activity, so there are also many options for blood testing. One of them is serological blood tests. This is a basic analysis carried out in order to recognize 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 amount of antibodies against viruses and microbes in the body. To do this, the antigen of the causative agent of the disease is added to the blood serum, after which the ongoing chemical reaction is evaluated;
- antigen detection by introducing antibodies into the blood;
- blood type determinations.
Serological blood tests are always ordered twice - to determine the dynamics of the disease. A single determination of the interaction of antigens and antibodies indicates only the fact of infection. To reflect the fullpictures where one can observe an increase in the number of connections between immunoglobulins and antigens, a re-examination is needed.
Serological studies: analyzes and their interpretation
An increase in the number of antigen-antibody complexes in the body indicates the presence of an infection in the patient's body. Carrying out 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 test already indicates the detection of symptoms of a particular infection.
What can affect the result of the analysis
You should carefully monitor the conditions in which blood is taken. It is impossible to allow something foreign to enter the blood. The day before the analysis, you should not overload the body with fatty foods, alcohol and sugary drinks. Avoid stressful situations and reduce physical activity. Biological material should get to the laboratory as soon as possible, since long-term storage of serum leads to partial inactivity of antibodies.
Serological research methods
In laboratory practice, serological blood testing is complementary to bacteriological testing. The main methods are presented:
1. Fluorescence reaction, which is carried out in two stages. Antibodies are detected firstcirculating antigen complex. Then, 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. The results of the reactions are evaluated using a fluorescent microscope. The nature of the glow, the shape, and the size of objects are evaluated.
2. An agglutination reaction, which is a simple reaction of agglutination of discrete antigens with the help of antibodies. Highlight:
- direct reactions used to detect antibodies in the patient's blood serum. A certain amount of killed microbes is added to the serum and causes the formation of a precipitate in the form of flakes. Serological testing for typhoid fever involves a direct agglutination test;
- passive hemagglutonation reactions based on the ability of erythrocytes to adsorb the antigen on its surface and cause sticking when it comes into contact with the antibody, and visible precipitation. It is used in the process of diagnosing infectious diseases to detect hypersensitivity to certain drugs. When evaluating the results, the appearance of the sediment is taken into account. A precipitate in the form of a ring at the bottom of the tube indicates a negative reaction. A lacy precipitate with jagged edges indicates the presence of an infection.
3. Enzyme immunoassay, which is based on the principle of attaching an enzyme label to antibodies. This allows you to see the result of the reaction by the appearance of an enzymeactivity or by changing its level. This research method has a number of advantages:
- very sensitive;
- used reagents are universal and they are stable for half a year;
- the process of recording the results of the analysis is automated.
The above 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 the antigens of the pathogen even after treatment and the death of the bacteria that cause it.
Diagnostic value of the study
The results of serological tests are a valuable diagnostic tool, but have an auxiliary value. 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 be the basis for making a diagnosis. Such results should be taken into account when the patient had a similar disease in the past and received appropriate treatment.
Determination of hereditary signs of blood, confirmation or refutation of paternity, the study of hereditary and autoimmune diseases, establishing the nature and source of infection in epidemics - allthis helps to identify serological blood tests. The interpretation of the results provides information on the presence of specific proteins for infections such as syphilis, hepatitis, HIV, toxoplasmosis, rubella, measles, typhoid fever.
