An enzyme-linked immunosorbent assay or ELISA is a medical test that can detect certain viruses, toxins and other substances by using a combination of antibodies and dies. It consists of a plate with small indentations into which a sample is placed. If the sample contains a substance to which the antigens bind, it changes colour to indicate its presence.
ELISA is widely used due to its low cost and convenience compared to a radioimmunoassay and its very high sensitivity. It first came into widespread use to identify patients infected with the HIV virus but can detect many conditions including substances associated with tuberculosis, rotavirus, hepatitis and e. coli.