How does direct ELISA work?

Direct ELISA workflow diagram

In a direct ELISA, the target antigen is immobilized on the microplate well and detected by an enzyme-conjugated primary antibody. When substrate is added, the linked enzyme generates a measurable signal.

Because it uses a single detection antibody, direct ELISA offers fewer steps and a relatively fast workflow. However, it generally provides less signal amplification than indirect or sandwich ELISA.