Enzyme-linked immunosorbent assay is a biochemical analysis technique used to detect the presence of a protein in a fluid sample. The assay uses two antibodies, one that specifically detects the protein of interest, and a second antibody that reacts to the first antibody-protein complex. The second antibody is usually linked to an enzyme that produces a chromogenic or fluorogenic substrate, thus providing the read-out for the assay. ELISAs are often used to measure cancer biomarkers in the blood of cancer patients.

 Osteopontin