Enzyme Immunoassay

Points To Remember

  • The enzyme immunoassay (EIA) is of two types. They are homogeneous EIA and heterogeneous EIA.
  • Homogeneous EIA is a homogeneous assay in the sense that it never requires any washing steps. All the reagents are added at a time and the result are read, e.g. enzyme-multiplied immunoassay technique (EMIT).
  • In heterogenous EIA, the reagents are added in different steps interrupted by washing procedure, e.g. enzyme-linked immunosorbent assay (ELISA).
  • EMIT is a common method for screening urine and blood for drugs, whether legal or illicit.
  • ELISA or enzyme linked immunosorbent assay is an immunoassay technique involving the reaction of antigen and antibody in vitro.
  • Direct ELISA uses the method of directly labelling the specific antibody.
  • Indirect ELISA utilizes an unlabelled primary antibody (specific antibody) in conjunction with  labelled secondary antibody.
  • IgM antibody-capture ELISA (MAC ELISA) has been developed to detect specific IgM isotype antibodies.