What is the ELISA measurement method?

ELISA stands for “Enzyme-linked Immunosorbent Assay”. It is the standard scientific method used by laboratories to detect antibodies in the blood. ELISA is used, for example, in allergy tests or in the diagnosis of infectious diseases and is also the established laboratory measurement for antibody tests against SARS-CoV-2.

A special laboratory plate is coated with the virus (the antigen), then your sample is added. If there are antibodies in the sample, complexes of antibody and antigen will now form on the plate after some time.

The laboratory then adds a special enzyme that is also bound to an antibody. If antibody-antigen complexes were previously formed on the plate, the new enzyme-antibody entities dock onto them. The larger complex that results is called an “ELISA sandwich.”

When these “sandwiches” form, a chemical substance added to the enzyme converts into a dye that can be seen on the plate. How intense this color later turns out indicates whether there are antibodies in the sample and, if so, how many.