Serological tests

At the heart of all serological reactions is the interaction of Ar and AT.Serological reactions are used in two ways.

The first direction. Detection with the diagnostic purpose of AT in the serum of the subject. In this case, the constituents of the blood serum are unknown from the two components of the reaction( AT, Ar), since the reaction is performed with known Ar. A positive result of the reaction indicates the presence in the blood of AT, homologous to the applied Ar;a negative result indicates the absence of such. Reliable results are obtained by examining the paired blood serum of the patient taken at the onset of the disease( 3-7th day) and 10-12 days later. In this case, it is possible to observe the dynamics of AT growth. In viral infections, only a fourfold increase in the titer of AT in the second serum is of diagnostic importance.

With the introduction of ELISA into the practice of laboratories, it became possible to determine in the blood of patients the antibodies attributed to different classes of Ig( IgM and IgG), which significantly increased the informative value of serological diagnostic methods. In the case of the primary immune response, when the human immune system interacts with the infectious agent for the first time, primarily AT, attributed to IgM, is synthesized. Only later, on the 8th-12th day after the penetration of Ag into the body, ATG IgG begins to accumulate in the blood. In the immune response to infectious agents, the synthesis of ATA IgA, which plays an important role in protecting against infectious agents of the skin and mucous membranes, also occurs.

The second direction. Establishment of generic and species belonging to the microorganism. In this case, Ar becomes an unknown component of the reaction. Such a study requires a reaction with known immune sera.

Serological tests do not possess 100% sensitivity and specificity in the diagnosis of infectious diseases, can give cross-reactions with ATs directed to Arg of other pathogens. In connection with this, it is necessary to evaluate the results of serological studies with great care and taking into account the clinical picture of the disease. This is due to the use of a variety of tests for the diagnosis of one infection, as well as the use of the Western-blot method to confirm the results of screening methods.