What is Post zone?

The postzone is the comparable zone of antigen excess.In some titrations, however (such as the slide latex agglutination test for cryptococcal antigen), antigen is varied in the presence of a constant amount of antibody (Fig 2, bottom).

What causes Prozone?

The prozone phenomenon, seen during primary and secondary syphilis, occurs because a higher than optimal amount of antibody in the tested sera prevents the flocculation reaction typifying a positive result in reagin tests. Serum dilution is necessary to make the correct diagnosis.

What is the difference between Prozone and Postzone phenomenon?

Prozone – excess antibody to the available amount of antigen (no agglutination is a result) Zone of Equivalence – optimal amounts of both antibody and antigen (results in agglutination) Postzone – excess antigen to the available antibody (no agglutination is a result)

What is Prozone limit?

The hook effect or the prozone effect is an immunologic phenomenon whereby the effectiveness of antibodies to form immune complexes is sometimes impaired when concentrations of an antibody or an antigen are very high.

What is Post zone effect?

The Post-zone Phenomenon is a false-negative test caused by excessive antigen, relative to antibodies, which prevents antibody-to-antigen crosslinking [4]. Crosslinking is necessary for immunochromatographic detection [4].

What is the zone of equivalence?

: the part of the range of possible proportions of interacting antibody and antigen in which neither or but small traces of both remain uncombined in the medium.

How common is prozone effect?

Results. Our results showed that the incidence of the prozone phenomenon was low (0.83%) and could occur during any clinical phase, particularly during primary and secondary syphilis. Pregnancy and neurosyphilis were associated with the prozone phenomenon; sex, age, and whether the patient had been treated were not.

What causes hook effect?

The hook effect occurs when blood, urine, or other samples contain too much of the substance that the specific pregnancy test is trying to detect. Instead of giving a positive result, the laboratory test becomes overwhelmed by the excess substance and provides a false-negative result.

What is zone of equivalence?

What is Prozone and Postzone effect?

When there is excess amount of antibody or excess amount of antigen, the insoluble structure cannot be formed and the soluble complex fails to generate the desirable results. When antibody is in excess, we call it the prozone effect. When the antigen is in excess, we call it the postzone effect.

How common is Prozone effect?

Why the competitive format is not affected by the hook effect?

The hook effect does not occur in competitive immunoassays. That means that in reaction there is a surplus on analytes that did not penetrate to analyte-antibody complex compound. This results in falsely decreased value of the measured analyte which could even lie in the reference interval.

Is the zone of antibody excess called the post zone?

The zone of antibody excess is known as the prozone phenomenon and the zone of antigen excess is known as post zone phenomenon. In the prozone phenomenon, there is too much antibody for efficient lattice formation.

When does the Prozone and postzone phenomenon occur?

In the case of antibody excess, the prozone phenomenon occurs, in which antigen combines with only one or two antibody molecules, and so no cross-linkages are formed. At the other side of the zone, where there is antigen excess, the postzone phenomenon occurs,…

What causes an antibody reaction below the prozone?

As the antibody concentration is lowered below the prozone, the reaction occurs. This phenomenon may be due simply to antibody excess or it may be due to blocking antibody or to nonspecific inhibitors in serum.

Which is the zone of antibody excess in a titration?

  In most titrations, the amount of antibody is varied in the presence of a constant amount of antigen (Fig 2, top). The prozone is then the zone of antibody excess, resulting in an absence of antibody-antigen precipitation or agglutination. The postzone is the comparable zone of antigen excess.