ELISA test is stand for Enzyme-linked immunosorbent Assay which also known as Enzyme immunoassay (EIA), contains an enzyme-antibody complex that can be used as a color tracer for antigen-antibody reactions. The enzymes used most often are horseradish and alkaline phosphatase, both of which release a dye (chromogen) when exposed to their substrate. This technique also relies on a solid support such as a plastic micro titer plate that can absorb (attract on its surface) the reactants.
The Indirect ELISA test can detect antibodies in a serum sample. As with other indirect test, the final positive reaction is achieved by means of an antibody-antibody reaction. The indicator antibody is complexed to an enzyme that produces a color change with positive serum sample. The starting reactant is a known antigen that is absorbed to the surface of a well. To this, unknown serum is added. After rinsing, an enzyme-Ab reagent that can react with the unknown test antibody is placed in the well. The substrate to the enzyme is then added, and the wells are scanned for color changes. Color development indicates that all the components reacted and that the antibody was present in the patient's serum. This is he common screening test for the antibodies to HIV (AIDS virus), various rickettsial species, hepatitis A and C, the cholera false positives can occur, a verification test may be necessary (such as Western blot for HIV).
The Capture ELISA or Direct ELISA or sandwich test, a known antibody is adsorbed to the bottom of a well and incubated with a solution containing unknown antigen. After excess unbound components have been rinsed off, an enzyme-antibody indicator that can react with the antigen added. If antigen is present, it will attract the indicator-antibody and hold it in place. Next, the substrate to the enzyme is placed in the wells and incubated. Enzymes affixed to the antigen will hydrolyze the substrate and release a colored dye. Thus, any color developing in the wells is a positive result. Lack of color means that the antigen was not present and that capture technique is used to detect antibodies to hantavirus, rubella virus, and Toxoplasma.
A newer technology uses electronic monitors that directly read out antibody-antigen reactions. Without belaboring the technical aspects, these systems contain computer chips that sense the minute changes
The Indirect ELISA test can detect antibodies in a serum sample. As with other indirect test, the final positive reaction is achieved by means of an antibody-antibody reaction. The indicator antibody is complexed to an enzyme that produces a color change with positive serum sample. The starting reactant is a known antigen that is absorbed to the surface of a well. To this, unknown serum is added. After rinsing, an enzyme-Ab reagent that can react with the unknown test antibody is placed in the well. The substrate to the enzyme is then added, and the wells are scanned for color changes. Color development indicates that all the components reacted and that the antibody was present in the patient's serum. This is he common screening test for the antibodies to HIV (AIDS virus), various rickettsial species, hepatitis A and C, the cholera false positives can occur, a verification test may be necessary (such as Western blot for HIV).
The Capture ELISA or Direct ELISA or sandwich test, a known antibody is adsorbed to the bottom of a well and incubated with a solution containing unknown antigen. After excess unbound components have been rinsed off, an enzyme-antibody indicator that can react with the antigen added. If antigen is present, it will attract the indicator-antibody and hold it in place. Next, the substrate to the enzyme is placed in the wells and incubated. Enzymes affixed to the antigen will hydrolyze the substrate and release a colored dye. Thus, any color developing in the wells is a positive result. Lack of color means that the antigen was not present and that capture technique is used to detect antibodies to hantavirus, rubella virus, and Toxoplasma.
A newer technology uses electronic monitors that directly read out antibody-antigen reactions. Without belaboring the technical aspects, these systems contain computer chips that sense the minute changes
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