Which test has the greatest sensitivity for antigen detection?

The ELISA (Enzyme-Linked Immunosorbent Assay) is recognized for its high sensitivity in detecting antigens. This sensitivity stems from its design, which allows for the amplification of signals through enzyme-substrate reactions, resulting in a measurable outcome even at very low antigen concentrations. ELISA employs specific antibodies that are linked to an enzyme, and when the target antigen is present, a color change occurs in the substrate, which is detectable with spectrophotometry. This capability makes ELISA particularly valuable in clinical settings for diagnosing infections and measuring biomolecules.

In contrast, while other tests like Western Blot are useful for detecting specific proteins and confirming positive results, they typically lack the sensitivity of ELISA, especially in initial screening stages. Radioimmunoassay, although sensitive, is less commonly used today due to safety concerns related to radioactivity. Immunofluorescence is effective for visualizing antigens in tissue sections or cell cultures but generally exhibits lower sensitivity compared to ELISA for quantifying circulating antigens in serum or other bodily fluids. Therefore, the high sensitivity of ELISA makes it the most suitable choice for antigen detection among the options provided.