HOOK effect, refers to the phenomenon of false negatives due to the inappropriate proportion of antigen-antibody, in which the excess of antibody is called the prozone effect; the excess of antigen is called the posterior band effect.
When the antigen-antibody reacts specifically, the amount of the conjugate formed is related to the concentration of the reactant. Whether a different amount of antigen is added to a certain amount of antibody or a different amount of antibody is added to a certain amount of antigen, it can be found that the strongest antigen-antibody reaction occurs only when the molecular ratios of the two are appropriate.
Before and after the equivalence band, antibodies and antigen excess affect the formation of precipitates. This phenomenon is called a zone phenomenon. Banding often occurs in clinical tests, especially in ELISA reactions. When there is an excess of antibody, it is called a prezone, and when there is an excess of antigen, it is called a postzone. Therefore, in the clinical work, we must pay attention to the phenomenon of anterior and posterior band, so as to avoid false negative results, especially the previous band effect is obvious, this situation can be solved by further diluting the sample.