ELISA Measurements

Test ELISA Laboratory

What is ELISA?

Enzyme-linked immunosorbent assay (ELISA) is a plate-based assay that detects and quantifies peptides, proteins, antibodies and hormones. 

This assay is depend on specific antibodies to bind the target antigen and a detection system to indicate the presence and quantity of antigen binding. 

Applicability

ELISA can be used to:

• detect the presence of allergens in food
• determination of concentrations of illicit drugs
• monitor the levels of pharmaceutical concentrations of drugs (medicines)
• pregnancy test
• diagnosis of various diseases that induce the production of immunoglobulins, such as infectious, autoimmune diseases or allergies.

How is the procedure?

In this assay, an antigen is immobilized to a solid surface and then complexed with an antibody that is linked to an enzyme. The detection is accomplished by assessing the conjugated enzyme activity via incubation with a substrate to produce a measurable product. 

The most important element of the detection strategy is a highly specific antibody-antigen interaction. 

The next figure summarizes the ELISA method steps.

Modifications in basic procedure

ELISA can be performed with some modifications to the basic procedure: 

Direct - uses a labeled primary antibody that reacts directly with the antigen. The immobilization of the antigen of interest is done by direct adsorption to the assay plate.

Indirect - uses a labeled secondary antibody for detection. The immobilization of the antigen of interest is done indirectly via a capture antibody that has been attached to the plate

Sandwich - the analyte to be measured is bound between two primary antibodies (the capture and the detection antibody). 

Competitive - is commonly used when the antigen is small and has only one epitope, or antibody binding site.