ELISA diagnosis of infections is an enzyme-linked immunosorbent assay, which is increasingly used in medicine. It is based on the detection of characteristic antibodies in the patient's body or on the detection of antigens of the causative agent of the disease.
Antigens are called substances that, when ingested, cause a protective reaction of the immune system, when infected, it begins to produce special proteins - antibodies.
Each pathogen has its own set of antigens, identifying them, the doctor can make a "portrait" of the suspected microorganism. The immune system also works selectively and produces antibodies for a particular virus, and they will not interact with antigens of another pathogen.
The mechanism by which ELISA diagnosis is possible is the reaction of antigens to introduced antibodies; as a result of this reaction, an antibody-antigen complex is formed. Where do antibodies or antigens come from to carry out such a reaction? Everything is very simple, they are produced industrially for each type of research. Each type of antigen or antibody is labeled with a special enzyme in the factory. Thus, during the formation of the antibody-antigen complex, it will have a label in its composition, and when a coloring reagent is added, due to the presence of this label, all the complexes that appear will change their color.
When ELISA diagnostics of a sample is carried out, the intensity of staining of antibodies and antigens in the material used for diagnostics is examined, and special equipment calculates their quantity.
IFA results
If infection antigens or antibodies are detected, what does this mean? This means that the patient definitely has an infection. Moreover, ELISA diagnostics can give the name of a specific microorganism responsible for the appearance of this antigen with high accuracy. Interestingly, unlike virological or bacteriological diagnostic methods, the weak viability of the virus will not interfere with its determination.
But there is another side to this coin, if the ELISA in the test sample detected antibodies that clearly indicate patient contact with the pathogen, this cannot guarantee that the microorganism is still present in the human body. After all, antibodies can remain quite a long time in the patient’s body, even after recovery. A negative ELISA result from a single check for antibodies is also not always reliable. For the immune response to occur, the body needs time, which is why a repeat analysis of the samples is carried out two to three weeks after the first for an accurate diagnosis. And that is why ELISA diagnosis of most of the known infections makes sense no earlier than three weeks after infection.
The advantages of enzyme immunoassay for the diagnosis of infectious diseases
Analysis by immunofermentation has a number of advantages, thanks to which it has become so popular in recent years.
With its help, it became possible to diagnose a wide range of various infections. For example, viral infections (cytomegalovirus, HIV, herpes, hepatitis), most sexually transmitted infections (mycoplasmosis, syphilis, chlamydia, ureaplasmosis), as well as borreliosis, tick-borne encephalitis and others.
A short period for which it is possible to conduct a study, especially if it is necessary to identify the pathogen antigen or determine the level of antibodies once. As a rule, this type of analysis requires one to three days.
ELISA diagnostics can be used in those cases when microscopy or culture are associated with great difficulties or even impossible.
It is able to assess the effectiveness of the patient’s immune response to the introduction of the pathogen.
Having identified the ratio of different classes of immunoglobulins, the physician will be able to determine at what stage the disease is currently at, the importance of this information can hardly be overestimated.
All these advantages have made ELISA diagnostics an indispensable assistant of modern medicine.