Enzyme immunoassay
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Description:
The enzyme immunoassay, or IFA (English Enzyme-Linked ImmunoSorbent Assay, ELISA) is a laboratory immunological method of high-quality definition and quantitative measurement of antigens, and also immunoglobulins and hormones.
The IFA method has high sensitivity and specificity which makes more than 90% now.
Test systems for immunoenzymatic diagnosis reveal a wide range of various infections: HIV infection, viral hepatitis, Cytomegaloviral, gerpesny, toksoplazmenny, etc.
The method of an enzyme immunoassay (IFA) gives the chance of definition of antibodies (IgG, IgA, IgM) to contagiums in blood. These antibodies are developed by an organism in response to infection. Antibodies come to light at interaction with the special drugs containing the corresponding antigens forming a strong complex which can be found in the different ways with antibodies.
The principle of interaction of an immunoadsorbent — contagium antigen with the revealed antibodies is the cornerstone of a method. Depending on what antibodies are used, the test system will reveal in the studied sample or specific antibodies irrespective of their class, or an antibody only of a certain class. As material for a research serves serum or plasma of the venous blood taken on an empty stomach.
For diagnosis of venereal diseases three classes of immunoglobulins are used: M, A, G.
Thanks to the fact that immunoglobulins of different classes are produced in a certain sequence by means of IFA it is possible to diagnose an infection at different stages and to trace dynamics of development of process.
Sequence of production of immunoglobulins of different classes following:
The first IgM-antibodies appear. As a rule, it occurs in 1–3 weeks from the moment of infection. Time of detection of antibodies depends both on the infection, and on features of immune system of the specific person. There are symptoms of an acute infection. Detection of IgM-antibodies in the analysis indicates existence of an acute phase of a disease or an exacerbation of chronic infectious diseases.
In a month IgA-antibodies which main part concentrates on mucous membranes where their protective function is implemented begin to be developed.
The last IgG-antibodies, as a rule, for the 4th week from the moment of infection appear. After treatment of clamidiosis, mycoplasmosis, trichomoniasis their level considerably decreases as immunity against these diseases does not develop.
It is necessary to pay attention that detection of immunoglobulins (IgM, IgG, IgA) indicates only existence of antibodies, but not existence of the activator. Therefore in certain cases the enzyme immunoassay can yield also false results — both false positive, and lozhnootratsatelny. However, specificity of the IFA best test systems of recombinant type approaches 100% now.
Thus, due to undoubted advantages of an enzyme immunoassay: conveniences in work, speed, objectivity due to automation of the accounting of results, a possibility of a research of immunoglobulins of various classes (what is important for early diagnosis of diseases and their forecast) is one of the main methods of laboratory diagnosis now.
IFA advantages — a possibility of early diagnosis of an infection, an opportunity to trace dynamics of development of process, speed and convenience in work.
Lack of IFA — treating indirect diagnostic methods, it allows to define an immune response of an organism on the activator, but not the activator.
