What is Post zone phenomenon?
What is Post zone phenomenon?
Postzone phenomenon is defined as a false-negative test resulting from high antigen titre, which interferes with the formation of the antigen-antibody lattice, necessary to visualize a positive test.
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 phenomenon when does it occur?
The prozone phenomenon generally refers to a false-negative response arising from cases in which high antibody titers interfere with the antigen-antibody lattice network formation that is necessary for visualizing a positive flocculation test.
What is meant by prozone effect?
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.
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.
What is 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 do I get rid of prozone?
EDTA eliminates the prozone effect because, as an iron-chelating reagent, it can inhibit the formation of C1qrs complement complex and prevent complement cascade activation . DTT disrupts the pentameric structure of IgM and the disulfide bonds in complement molecules, thus reducing the prozone effect .
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.
How can Prozone affect CRP results?
If CRP level is very high (in the range of 20 mg) agglutination may fail to appear due to antigen excess (prozone). When serum is drawn from a patient and tested at appropriate time intervals, changes in the level of C-reactive protein can be used as an index of recovery.
What is the meaning and outcome of a Prozone reaction in an agglutination assay?
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 the importance of zone of equivalence?
As more antigen is added, the reaction enters the equivalence zone (or zone of equivalence), where both the optimal antigen-antibody interaction and maximal precipitation occur. If even more antigen were added, the amount of antigen would become excessive and actually cause the amount of precipitation to decline.
What is the equivalence zone of equivalence point?
As more antigen is added, the amount of protein precipitated increases until the antigen/antibody molecules are at an optimal ratio. This is known as the zone of equivalence or equivalence point. When the amount of antigen in solution exceeds the amount of antibody, the amount of precipitation will decrease.
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 does Prozone stand for in medical terms?
/pro·zone/ (pro´zōn) the phenomenon exhibited by some sera, in which agglutination or precipitation occurs at higher dilution ranges, but is not visible at lower dilutions or when undiluted.
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.
When does an agglutination occur in the prozone?
Also found in: Wikipedia . in an agglutination or precipitation reaction, the zone of relatively high antibody concentrations within which no reaction occurs. As the antibody concentration is lowered below the prozone, the reaction occurs.
What is the meaning of the prozone phenomenon?
Prozone phenomenon. 2. • Prozone phenomena • In an agglutination or precipitation reaction, the zone of relatively high antibody concentrations within which no reaction occurs.
How is precipitation prevented in the Prozone and postzone zones?
Precipitation Curve (Prozone and Postzone) On either side of the equivalence zone, precipitation is actually prevented because of an excess of either antigen or antibody. 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.
Is the prozone zone in the agglutination reaction?
2. • Prozone phenomena • In an agglutination or precipitation reaction, the zone of relatively high antibody concentrations within which no reaction occurs.
What happens at the other side of the postzone?
At the other side of the zone, where there is antigen excess, the postzone phenomenon occurs, in which small aggregates are surrounded by excess antigen, and again no lattice network is formed. In addition to the affinity and avidity of the antibody involved, precipitation depends on the relative proportions of antigen and antibody present.