What is Postzone 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 causes prozone phenomenon?

Prozone phenomenon is a very rare and false negative reaction and occurs due to disproportionately increased antibodies in a specimen. Immune system is responsible for excess antibodies. It is frequently seen in HIV, neurosyphilis, early syphilis (mainly secondary syphilis).

What is prozone phenomenon in syphilis?

Prozone phenomenon is a false negative response resulting from high antibody titer which interferes with formation of antigen- antibody lattice, necessary to visualize a positive flocculation test.

What is prozone effect in agglutination?

However, excess antibodies in a serum sample can inhibit the antigen-antibody interaction and subsequent agglutination reaction, leading to a false negative result, which is known as a prozone phenomenon or effect (Tizard 2004).

What is a precipitin reaction?

THE precipitin reaction is also known as the “biological reaction” for proteins; it enables us to distinguish between proteins by using the animal body as a test-tube, and to establish differences between them which no other form of test-tube will detect.

What causes hook effect in Elisa assay?

The high-dose hook effect is confined to one-stage immunometric (sandwich) assays, giving a decrease in signal at very high concentrations of analyte (see Fig. 8). It is caused by excessively high concentrations of analyte simultaneously saturating both capture and detecting antibodies.

What is meant by prozone?

[ prō′zōn′ ] n. The phenomenon in which mixtures of specific antigen and antibody do not agglutinate or precipitate visibly because of an excess of either antibody or antigen.

How can prozone phenomenon be overcome?

It can be overcome by appropriate dilution and titration of antisera. We have observed that by simply washing the RBCs once more after the antiglobulin phase the prozone phenomenon is elimi- nated, and the strength of agglutination of RBCs (i.e., the sensitivity of the test) is con- siderably increased.

How is a prozone phenomenon corrected?

Simple dilution of the sample will correct this effect.

Which of following is true about prozone phenomenon?

Which of following is true about prozone phenomenon? It is due to disproportionate antigen and antibody levels. There is no relation with antigen and antibody levels. It is due to proportionate antigen and antibody levels.

What is prozone and Postzone?

The prozone reaction refers to the absence of antibody-antigen precipitation in the presence of antibody excess. Since the authors refer to situations of antigen excess, the term prozone cannot correctly be used. Instead, absence of precipitation with excess antigen is described as the postzone phenomenon.

What is prozone in chemistry?

2.11 Prozone (or “Hook”) Effect The Prozone or hook effect is observed when a very high amount of an analyte is present in the sample but the observed value is falsely lowered. This type of interference is observed more commonly in sandwich assays.