What is an Indirect ELISA?

In an indirect ELISA, the antigen is bound to the bottom of the microplate well and detected using a primary antibody specific to the antigen, followed by an enzyme‑conjugated secondary antibody that binds to the primary antibody.

This format introduces an additional amplification step, which can increase assay sensitivity and flexibility. Indirect ELISA is commonly used when enhanced signal detection is needed or when multiple primary antibodies are used across experiments.