Q.ELISA is mainly used for :

ELISA is a diagnostic immunoassay used to detect pathogens (or the antibodies a host has made against them) in blood or other body fluids.

ELISA works on the principle of highly specific antigen-antibody interaction: a sample is tested against a known antigen or antibody bound to a solid surface (such as a microtitre-plate well), and an enzyme-linked detection system produces a measurable colour change if the target antigen (from a pathogen) or antibody (produced by the host against a pathogen) is present. This makes ELISA an extremely useful and widely used diagnostic tool for detecting infections -- for example, it is a standard screening test for HIV, h …